From 6480bed441a03d6346b9439112ee4b9aeee7cbc4 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?St=C3=A9phane=20Bidoul?= <stephane.bidoul@gmail.com>
Date: Mon, 21 Dec 2020 12:38:41 +0100
Subject: [PATCH 1/9] Revert "Remove on_returncode parameter from
 call_subprocess"

This reverts commit ab3ee7191ca47294f8827916180969e23f5e0381.
---
 src/pip/_internal/vcs/git.py            | 10 ++----
 src/pip/_internal/vcs/mercurial.py      |  1 +
 src/pip/_internal/vcs/versioncontrol.py | 42 ++++++++++++++++---------
 3 files changed, 32 insertions(+), 21 deletions(-)

diff --git a/src/pip/_internal/vcs/git.py b/src/pip/_internal/vcs/git.py
index 1831aede5..141263803 100644
--- a/src/pip/_internal/vcs/git.py
+++ b/src/pip/_internal/vcs/git.py
@@ -135,13 +135,8 @@ class Git(VersionControl):
           rev: the revision name.
         """
         # Pass rev to pre-filter the list.
-
-        output = ''
-        try:
-            output = cls.run_command(['show-ref', rev], cwd=dest)
-        except SubProcessError:
-            pass
-
+        output = cls.run_command(['show-ref', rev], cwd=dest,
+                                 on_returncode='ignore')
         refs = {}
         for line in output.strip().splitlines():
             try:
@@ -420,6 +415,7 @@ class Git(VersionControl):
             r = cls.run_command(
                 ['rev-parse', '--show-toplevel'],
                 cwd=location,
+                on_returncode='raise',
                 log_failed_cmd=False,
             )
         except BadCommand:
diff --git a/src/pip/_internal/vcs/mercurial.py b/src/pip/_internal/vcs/mercurial.py
index 69763feae..b7f8073fd 100644
--- a/src/pip/_internal/vcs/mercurial.py
+++ b/src/pip/_internal/vcs/mercurial.py
@@ -144,6 +144,7 @@ class Mercurial(VersionControl):
             r = cls.run_command(
                 ['root'],
                 cwd=location,
+                on_returncode='raise',
                 log_failed_cmd=False,
             )
         except BadCommand:
diff --git a/src/pip/_internal/vcs/versioncontrol.py b/src/pip/_internal/vcs/versioncontrol.py
index 6724dcc69..5b93b6609 100644
--- a/src/pip/_internal/vcs/versioncontrol.py
+++ b/src/pip/_internal/vcs/versioncontrol.py
@@ -90,6 +90,7 @@ def make_vcs_requirement_url(repo_url, rev, project_name, subdir=None):
 def call_subprocess(
     cmd,  # type: Union[List[str], CommandArgs]
     cwd=None,  # type: Optional[str]
+    on_returncode='raise',  # type: str
     extra_environ=None,  # type: Optional[Mapping[str, Any]]
     extra_ok_returncodes=None,  # type: Optional[Iterable[int]]
     log_failed_cmd=True  # type: Optional[bool]
@@ -157,21 +158,32 @@ def call_subprocess(
         proc.returncode and proc.returncode not in extra_ok_returncodes
     )
     if proc_had_error:
-        if not showing_subprocess and log_failed_cmd:
-            # Then the subprocess streams haven't been logged to the
-            # console yet.
-            msg = make_subprocess_output_error(
-                cmd_args=cmd,
-                cwd=cwd,
-                lines=all_output,
-                exit_status=proc.returncode,
+        if on_returncode == 'raise':
+            if not showing_subprocess and log_failed_cmd:
+                # Then the subprocess streams haven't been logged to the
+                # console yet.
+                msg = make_subprocess_output_error(
+                    cmd_args=cmd,
+                    cwd=cwd,
+                    lines=all_output,
+                    exit_status=proc.returncode,
+                )
+                subprocess_logger.error(msg)
+            exc_msg = (
+                'Command errored out with exit status {}: {} '
+                'Check the logs for full command output.'
+            ).format(proc.returncode, command_desc)
+            raise SubProcessError(exc_msg)
+        elif on_returncode == 'warn':
+            subprocess_logger.warning(
+                'Command "{}" had error code {} in {}'.format(
+                    command_desc, proc.returncode, cwd)
             )
-            subprocess_logger.error(msg)
-        exc_msg = (
-            'Command errored out with exit status {}: {} '
-            'Check the logs for full command output.'
-        ).format(proc.returncode, command_desc)
-        raise SubProcessError(exc_msg)
+        elif on_returncode == 'ignore':
+            pass
+        else:
+            raise ValueError('Invalid value: on_returncode={!r}'.format(
+                             on_returncode))
     return ''.join(all_output)
 
 
@@ -764,6 +776,7 @@ class VersionControl(object):
         cls,
         cmd,  # type: Union[List[str], CommandArgs]
         cwd=None,  # type: Optional[str]
+        on_returncode='raise',  # type: str
         extra_environ=None,  # type: Optional[Mapping[str, Any]]
         extra_ok_returncodes=None,  # type: Optional[Iterable[int]]
         log_failed_cmd=True  # type: bool
@@ -777,6 +790,7 @@ class VersionControl(object):
         cmd = make_command(cls.name, *cmd)
         try:
             return call_subprocess(cmd, cwd,
+                                   on_returncode=on_returncode,
                                    extra_environ=extra_environ,
                                    extra_ok_returncodes=extra_ok_returncodes,
                                    log_failed_cmd=log_failed_cmd)

From 6693a71e0a472533714351b46aed688e19a17874 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?St=C3=A9phane=20Bidoul?= <stephane.bidoul@gmail.com>
Date: Mon, 21 Dec 2020 12:44:23 +0100
Subject: [PATCH 2/9] Revert "Remove show_stdout from run_command args"

This reverts commit 94882fd1ed9171ea5a2f4b8904dbd8763f05ba68.
---
 src/pip/_internal/vcs/bazaar.py         |  7 ++--
 src/pip/_internal/vcs/git.py            | 19 +++++-----
 src/pip/_internal/vcs/mercurial.py      | 16 ++++----
 src/pip/_internal/vcs/subversion.py     |  9 +++--
 src/pip/_internal/vcs/versioncontrol.py | 50 +++++++++++++++++--------
 5 files changed, 62 insertions(+), 39 deletions(-)

diff --git a/src/pip/_internal/vcs/bazaar.py b/src/pip/_internal/vcs/bazaar.py
index 3180713f7..efe524492 100644
--- a/src/pip/_internal/vcs/bazaar.py
+++ b/src/pip/_internal/vcs/bazaar.py
@@ -55,7 +55,8 @@ class Bazaar(VersionControl):
 
         url, rev_options = self.get_url_rev_options(url)
         self.run_command(
-            make_command('export', location, url, rev_options.to_args())
+            make_command('export', location, url, rev_options.to_args()),
+            show_stdout=False,
         )
 
     def fetch_new(self, dest, url, rev_options):
@@ -92,7 +93,7 @@ class Bazaar(VersionControl):
 
     @classmethod
     def get_remote_url(cls, location):
-        urls = cls.run_command(['info'], cwd=location)
+        urls = cls.run_command(['info'], show_stdout=False, cwd=location)
         for line in urls.splitlines():
             line = line.strip()
             for x in ('checkout of branch: ',
@@ -107,7 +108,7 @@ class Bazaar(VersionControl):
     @classmethod
     def get_revision(cls, location):
         revision = cls.run_command(
-            ['revno'], cwd=location,
+            ['revno'], show_stdout=False, cwd=location,
         )
         return revision.splitlines()[-1]
 
diff --git a/src/pip/_internal/vcs/git.py b/src/pip/_internal/vcs/git.py
index 141263803..a6d1396fc 100644
--- a/src/pip/_internal/vcs/git.py
+++ b/src/pip/_internal/vcs/git.py
@@ -11,7 +11,7 @@ from pip._vendor.packaging.version import parse as parse_version
 from pip._vendor.six.moves.urllib import parse as urllib_parse
 from pip._vendor.six.moves.urllib import request as urllib_request
 
-from pip._internal.exceptions import BadCommand, SubProcessError
+from pip._internal.exceptions import BadCommand, InstallationError, SubProcessError
 from pip._internal.utils.misc import display_path, hide_url
 from pip._internal.utils.subprocess import make_command
 from pip._internal.utils.temp_dir import TempDirectory
@@ -79,7 +79,7 @@ class Git(VersionControl):
 
     def get_git_version(self):
         VERSION_PFX = 'git version '
-        version = self.run_command(['version'])
+        version = self.run_command(['version'], show_stdout=False)
         if version.startswith(VERSION_PFX):
             version = version[len(VERSION_PFX):].split()[0]
         else:
@@ -102,7 +102,7 @@ class Git(VersionControl):
         # and to suppress the message to stderr.
         args = ['symbolic-ref', '-q', 'HEAD']
         output = cls.run_command(
-            args, extra_ok_returncodes=(1, ), cwd=location,
+            args, extra_ok_returncodes=(1, ), show_stdout=False, cwd=location,
         )
         ref = output.strip()
 
@@ -121,7 +121,7 @@ class Git(VersionControl):
             self.unpack(temp_dir.path, url=url)
             self.run_command(
                 ['checkout-index', '-a', '-f', '--prefix', location],
-                cwd=temp_dir.path
+                show_stdout=False, cwd=temp_dir.path
             )
 
     @classmethod
@@ -136,7 +136,7 @@ class Git(VersionControl):
         """
         # Pass rev to pre-filter the list.
         output = cls.run_command(['show-ref', rev], cwd=dest,
-                                 on_returncode='ignore')
+                                 show_stdout=False, on_returncode='ignore')
         refs = {}
         for line in output.strip().splitlines():
             try:
@@ -310,7 +310,7 @@ class Git(VersionControl):
         # exits with return code 1 if there are no matching lines.
         stdout = cls.run_command(
             ['config', '--get-regexp', r'remote\..*\.url'],
-            extra_ok_returncodes=(1, ), cwd=location,
+            extra_ok_returncodes=(1, ), show_stdout=False, cwd=location,
         )
         remotes = stdout.splitlines()
         try:
@@ -344,7 +344,7 @@ class Git(VersionControl):
         if rev is None:
             rev = 'HEAD'
         current_rev = cls.run_command(
-            ['rev-parse', rev], cwd=location,
+            ['rev-parse', rev], show_stdout=False, cwd=location,
         )
         return current_rev.strip()
 
@@ -357,7 +357,7 @@ class Git(VersionControl):
         # find the repo root
         git_dir = cls.run_command(
             ['rev-parse', '--git-dir'],
-            cwd=location).strip()
+            show_stdout=False, cwd=location).strip()
         if not os.path.isabs(git_dir):
             git_dir = os.path.join(location, git_dir)
         repo_root = os.path.abspath(os.path.join(git_dir, '..'))
@@ -415,6 +415,7 @@ class Git(VersionControl):
             r = cls.run_command(
                 ['rev-parse', '--show-toplevel'],
                 cwd=location,
+                show_stdout=False,
                 on_returncode='raise',
                 log_failed_cmd=False,
             )
@@ -422,7 +423,7 @@ class Git(VersionControl):
             logger.debug("could not determine if %s is under git control "
                          "because git is not available", location)
             return None
-        except SubProcessError:
+        except InstallationError:
             return None
         return os.path.normpath(r.rstrip('\r\n'))
 
diff --git a/src/pip/_internal/vcs/mercurial.py b/src/pip/_internal/vcs/mercurial.py
index b7f8073fd..75e903cc8 100644
--- a/src/pip/_internal/vcs/mercurial.py
+++ b/src/pip/_internal/vcs/mercurial.py
@@ -8,7 +8,7 @@ import os
 
 from pip._vendor.six.moves import configparser
 
-from pip._internal.exceptions import BadCommand, SubProcessError
+from pip._internal.exceptions import BadCommand, InstallationError
 from pip._internal.utils.misc import display_path
 from pip._internal.utils.subprocess import make_command
 from pip._internal.utils.temp_dir import TempDirectory
@@ -47,7 +47,7 @@ class Mercurial(VersionControl):
             self.unpack(temp_dir.path, url=url)
 
             self.run_command(
-                ['archive', location], cwd=temp_dir.path
+                ['archive', location], show_stdout=False, cwd=temp_dir.path
             )
 
     def fetch_new(self, dest, url, rev_options):
@@ -92,7 +92,7 @@ class Mercurial(VersionControl):
     def get_remote_url(cls, location):
         url = cls.run_command(
             ['showconfig', 'paths.default'],
-            cwd=location).strip()
+            show_stdout=False, cwd=location).strip()
         if cls._is_local_repository(url):
             url = path_to_url(url)
         return url.strip()
@@ -103,7 +103,8 @@ class Mercurial(VersionControl):
         Return the repository-local changeset revision number, as an integer.
         """
         current_revision = cls.run_command(
-            ['parents', '--template={rev}'], cwd=location).strip()
+            ['parents', '--template={rev}'],
+            show_stdout=False, cwd=location).strip()
         return current_revision
 
     @classmethod
@@ -114,7 +115,7 @@ class Mercurial(VersionControl):
         """
         current_rev_hash = cls.run_command(
             ['parents', '--template={node}'],
-            cwd=location).strip()
+            show_stdout=False, cwd=location).strip()
         return current_rev_hash
 
     @classmethod
@@ -130,7 +131,7 @@ class Mercurial(VersionControl):
         """
         # find the repo root
         repo_root = cls.run_command(
-            ['root'], cwd=location).strip()
+            ['root'], show_stdout=False, cwd=location).strip()
         if not os.path.isabs(repo_root):
             repo_root = os.path.abspath(os.path.join(location, repo_root))
         return find_path_to_setup_from_repo_root(location, repo_root)
@@ -144,6 +145,7 @@ class Mercurial(VersionControl):
             r = cls.run_command(
                 ['root'],
                 cwd=location,
+                show_stdout=False,
                 on_returncode='raise',
                 log_failed_cmd=False,
             )
@@ -151,7 +153,7 @@ class Mercurial(VersionControl):
             logger.debug("could not determine if %s is under hg control "
                          "because hg is not available", location)
             return None
-        except SubProcessError:
+        except InstallationError:
             return None
         return os.path.normpath(r.rstrip('\r\n'))
 
diff --git a/src/pip/_internal/vcs/subversion.py b/src/pip/_internal/vcs/subversion.py
index eae09c196..a57e19751 100644
--- a/src/pip/_internal/vcs/subversion.py
+++ b/src/pip/_internal/vcs/subversion.py
@@ -133,7 +133,7 @@ class Subversion(VersionControl):
 
     @classmethod
     def _get_svn_url_rev(cls, location):
-        from pip._internal.exceptions import SubProcessError
+        from pip._internal.exceptions import InstallationError
 
         entries_path = os.path.join(location, cls.dirname, 'entries')
         if os.path.exists(entries_path):
@@ -166,12 +166,13 @@ class Subversion(VersionControl):
                 # are only potentially needed for remote server requests.
                 xml = cls.run_command(
                     ['info', '--xml', location],
+                    show_stdout=False,
                 )
                 url = _svn_info_xml_url_re.search(xml).group(1)
                 revs = [
                     int(m.group(1)) for m in _svn_info_xml_rev_re.finditer(xml)
                 ]
-            except SubProcessError:
+            except InstallationError:
                 url, revs = None, []
 
         if revs:
@@ -217,7 +218,7 @@ class Subversion(VersionControl):
         #   svn, version 1.12.0-SlikSvn (SlikSvn/1.12.0)
         #      compiled May 28 2019, 13:44:56 on x86_64-microsoft-windows6.2
         version_prefix = 'svn, version '
-        version = self.run_command(['--version'])
+        version = self.run_command(['--version'], show_stdout=True)
 
         if not version.startswith(version_prefix):
             return ()
@@ -300,7 +301,7 @@ class Subversion(VersionControl):
                 'export', self.get_remote_call_options(),
                 rev_options.to_args(), url, location,
             )
-            self.run_command(cmd_args)
+            self.run_command(cmd_args, show_stdout=False)
 
     def fetch_new(self, dest, url, rev_options):
         # type: (str, HiddenText, RevOptions) -> None
diff --git a/src/pip/_internal/vcs/versioncontrol.py b/src/pip/_internal/vcs/versioncontrol.py
index 5b93b6609..a4995c88f 100644
--- a/src/pip/_internal/vcs/versioncontrol.py
+++ b/src/pip/_internal/vcs/versioncontrol.py
@@ -34,12 +34,10 @@ from pip._internal.utils.urls import get_url_scheme
 
 if MYPY_CHECK_RUNNING:
     from typing import (
-        Any,
         Dict,
         Iterable,
         Iterator,
         List,
-        Mapping,
         Optional,
         Text,
         Tuple,
@@ -89,15 +87,17 @@ def make_vcs_requirement_url(repo_url, rev, project_name, subdir=None):
 
 def call_subprocess(
     cmd,  # type: Union[List[str], CommandArgs]
+    show_stdout=False,  # type: bool
     cwd=None,  # type: Optional[str]
     on_returncode='raise',  # type: str
-    extra_environ=None,  # type: Optional[Mapping[str, Any]]
     extra_ok_returncodes=None,  # type: Optional[Iterable[int]]
     log_failed_cmd=True  # type: Optional[bool]
 ):
     # type: (...) -> Text
     """
     Args:
+      show_stdout: if true, use INFO to log the subprocess's stderr and
+        stdout streams.  Otherwise, use DEBUG.  Defaults to False.
       extra_ok_returncodes: an iterable of integer return codes that are
         acceptable, in addition to 0. Defaults to None, which means [].
       log_failed_cmd: if false, failed commands are not logged,
@@ -105,16 +105,33 @@ def call_subprocess(
     """
     if extra_ok_returncodes is None:
         extra_ok_returncodes = []
-
-    # log the subprocess output at DEBUG level.
-    log_subprocess = subprocess_logger.debug
-
-    env = os.environ.copy()
-    if extra_environ:
-        env.update(extra_environ)
+    # Most places in pip use show_stdout=False.
+    # What this means is--
+    #
+    # - We log this output of stdout and stderr at DEBUG level
+    # as it is received.
+    # - If DEBUG logging isn't enabled (e.g. if --verbose logging wasn't
+    #   requested), then we show a spinner so the user can still see the
+    #   subprocess is in progress.
+    # - If the subprocess exits with an error, we log the output to stderr
+    #   at ERROR level if it hasn't already been displayed to the console
+    #   (e.g. if --verbose logging wasn't enabled).  This way we don't log
+    #   the output to the console twice.
+    #
+    # If show_stdout=True, then the above is still done, but with DEBUG
+    # replaced by INFO.
+    if show_stdout:
+        # Then log the subprocess output at INFO level.
+        log_subprocess = subprocess_logger.info
+        used_level = logging.INFO
+    else:
+        # Then log the subprocess output using DEBUG.  This also ensures
+        # it will be logged to the log file (aka user_log), if enabled.
+        log_subprocess = subprocess_logger.debug
+        used_level = logging.DEBUG
 
     # Whether the subprocess will be visible in the console.
-    showing_subprocess = True
+    showing_subprocess = subprocess_logger.getEffectiveLevel() <= used_level
 
     command_desc = format_command_args(cmd)
     try:
@@ -176,8 +193,10 @@ def call_subprocess(
             raise SubProcessError(exc_msg)
         elif on_returncode == 'warn':
             subprocess_logger.warning(
-                'Command "{}" had error code {} in {}'.format(
-                    command_desc, proc.returncode, cwd)
+                'Command "%s" had error code %s in %s',
+                command_desc,
+                proc.returncode,
+                cwd,
             )
         elif on_returncode == 'ignore':
             pass
@@ -775,9 +794,9 @@ class VersionControl(object):
     def run_command(
         cls,
         cmd,  # type: Union[List[str], CommandArgs]
+        show_stdout=True,  # type: bool
         cwd=None,  # type: Optional[str]
         on_returncode='raise',  # type: str
-        extra_environ=None,  # type: Optional[Mapping[str, Any]]
         extra_ok_returncodes=None,  # type: Optional[Iterable[int]]
         log_failed_cmd=True  # type: bool
     ):
@@ -789,9 +808,8 @@ class VersionControl(object):
         """
         cmd = make_command(cls.name, *cmd)
         try:
-            return call_subprocess(cmd, cwd,
+            return call_subprocess(cmd, show_stdout, cwd,
                                    on_returncode=on_returncode,
-                                   extra_environ=extra_environ,
                                    extra_ok_returncodes=extra_ok_returncodes,
                                    log_failed_cmd=log_failed_cmd)
         except OSError as e:

From eda67075c1669b298d82a9a0e4c5484d02ad41b8 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?St=C3=A9phane=20Bidoul?= <stephane.bidoul@gmail.com>
Date: Mon, 21 Dec 2020 13:03:11 +0100
Subject: [PATCH 3/9] Revert "Create call_subprocess just for vcs commands"

This reverts commit 8adbc216a647b6b349f1b7f1eaa9e71cd3108955.
---
 src/pip/_internal/exceptions.py         |   5 -
 src/pip/_internal/vcs/subversion.py     |  14 ++-
 src/pip/_internal/vcs/versioncontrol.py | 144 +++---------------------
 3 files changed, 25 insertions(+), 138 deletions(-)

diff --git a/src/pip/_internal/exceptions.py b/src/pip/_internal/exceptions.py
index 56482caf7..5a2d012a5 100644
--- a/src/pip/_internal/exceptions.py
+++ b/src/pip/_internal/exceptions.py
@@ -91,11 +91,6 @@ class CommandError(PipError):
     """Raised when there is an error in command-line arguments"""
 
 
-class SubProcessError(PipError):
-    """Raised when there is an error raised while executing a
-    command in subprocess"""
-
-
 class PreviousBuildDirError(PipError):
     """Raised when there's a previous conflicting build directory"""
 
diff --git a/src/pip/_internal/vcs/subversion.py b/src/pip/_internal/vcs/subversion.py
index a57e19751..2575872a7 100644
--- a/src/pip/_internal/vcs/subversion.py
+++ b/src/pip/_internal/vcs/subversion.py
@@ -25,7 +25,7 @@ _svn_info_xml_url_re = re.compile(r'<url>(.*)</url>')
 
 
 if MYPY_CHECK_RUNNING:
-    from typing import Optional, Tuple
+    from typing import Optional, Text, Tuple
 
     from pip._internal.utils.misc import HiddenText
     from pip._internal.utils.subprocess import CommandArgs
@@ -218,7 +218,17 @@ class Subversion(VersionControl):
         #   svn, version 1.12.0-SlikSvn (SlikSvn/1.12.0)
         #      compiled May 28 2019, 13:44:56 on x86_64-microsoft-windows6.2
         version_prefix = 'svn, version '
-        version = self.run_command(['--version'], show_stdout=True)
+        cmd_output = self.run_command(['--version'], show_stdout=False)
+
+        # Split the output by newline, and find the first line where
+        # version_prefix is present
+        output_lines = cmd_output.split('\n')
+        version = ''  # type: Text
+
+        for line in output_lines:
+            if version_prefix in line:
+                version = line
+                break
 
         if not version.startswith(version_prefix):
             return ()
diff --git a/src/pip/_internal/vcs/versioncontrol.py b/src/pip/_internal/vcs/versioncontrol.py
index a4995c88f..1d9cb08fe 100644
--- a/src/pip/_internal/vcs/versioncontrol.py
+++ b/src/pip/_internal/vcs/versioncontrol.py
@@ -6,15 +6,13 @@ import errno
 import logging
 import os
 import shutil
-import subprocess
 import sys
 
 from pip._vendor import pkg_resources
 from pip._vendor.six.moves.urllib import parse as urllib_parse
 
-from pip._internal.exceptions import BadCommand, InstallationError, SubProcessError
-from pip._internal.utils.compat import console_to_str, samefile
-from pip._internal.utils.logging import subprocess_logger
+from pip._internal.exceptions import BadCommand, InstallationError
+from pip._internal.utils.compat import samefile
 from pip._internal.utils.misc import (
     ask_path_exists,
     backup_dir,
@@ -23,21 +21,18 @@ from pip._internal.utils.misc import (
     hide_value,
     rmtree,
 )
-from pip._internal.utils.subprocess import (
-    format_command_args,
-    make_command,
-    make_subprocess_output_error,
-    reveal_command_args,
-)
+from pip._internal.utils.subprocess import call_subprocess, make_command
 from pip._internal.utils.typing import MYPY_CHECK_RUNNING
 from pip._internal.utils.urls import get_url_scheme
 
 if MYPY_CHECK_RUNNING:
     from typing import (
+        Any,
         Dict,
         Iterable,
         Iterator,
         List,
+        Mapping,
         Optional,
         Text,
         Tuple,
@@ -45,6 +40,7 @@ if MYPY_CHECK_RUNNING:
         Union,
     )
 
+    from pip._internal.cli.spinners import SpinnerInterface
     from pip._internal.utils.misc import HiddenText
     from pip._internal.utils.subprocess import CommandArgs
 
@@ -85,127 +81,6 @@ def make_vcs_requirement_url(repo_url, rev, project_name, subdir=None):
     return req
 
 
-def call_subprocess(
-    cmd,  # type: Union[List[str], CommandArgs]
-    show_stdout=False,  # type: bool
-    cwd=None,  # type: Optional[str]
-    on_returncode='raise',  # type: str
-    extra_ok_returncodes=None,  # type: Optional[Iterable[int]]
-    log_failed_cmd=True  # type: Optional[bool]
-):
-    # type: (...) -> Text
-    """
-    Args:
-      show_stdout: if true, use INFO to log the subprocess's stderr and
-        stdout streams.  Otherwise, use DEBUG.  Defaults to False.
-      extra_ok_returncodes: an iterable of integer return codes that are
-        acceptable, in addition to 0. Defaults to None, which means [].
-      log_failed_cmd: if false, failed commands are not logged,
-        only raised.
-    """
-    if extra_ok_returncodes is None:
-        extra_ok_returncodes = []
-    # Most places in pip use show_stdout=False.
-    # What this means is--
-    #
-    # - We log this output of stdout and stderr at DEBUG level
-    # as it is received.
-    # - If DEBUG logging isn't enabled (e.g. if --verbose logging wasn't
-    #   requested), then we show a spinner so the user can still see the
-    #   subprocess is in progress.
-    # - If the subprocess exits with an error, we log the output to stderr
-    #   at ERROR level if it hasn't already been displayed to the console
-    #   (e.g. if --verbose logging wasn't enabled).  This way we don't log
-    #   the output to the console twice.
-    #
-    # If show_stdout=True, then the above is still done, but with DEBUG
-    # replaced by INFO.
-    if show_stdout:
-        # Then log the subprocess output at INFO level.
-        log_subprocess = subprocess_logger.info
-        used_level = logging.INFO
-    else:
-        # Then log the subprocess output using DEBUG.  This also ensures
-        # it will be logged to the log file (aka user_log), if enabled.
-        log_subprocess = subprocess_logger.debug
-        used_level = logging.DEBUG
-
-    # Whether the subprocess will be visible in the console.
-    showing_subprocess = subprocess_logger.getEffectiveLevel() <= used_level
-
-    command_desc = format_command_args(cmd)
-    try:
-        proc = subprocess.Popen(
-            # Convert HiddenText objects to the underlying str.
-            reveal_command_args(cmd),
-            stdout=subprocess.PIPE,
-            stderr=subprocess.PIPE,
-            cwd=cwd
-        )
-        if proc.stdin:
-            proc.stdin.close()
-    except Exception as exc:
-        if log_failed_cmd:
-            subprocess_logger.critical(
-                "Error %s while executing command %s", exc, command_desc,
-            )
-        raise
-    all_output = []
-    while True:
-        # The "line" value is a unicode string in Python 2.
-        line = None
-        if proc.stdout:
-            line = console_to_str(proc.stdout.readline())
-        if not line:
-            break
-        line = line.rstrip()
-        all_output.append(line + '\n')
-
-        # Show the line immediately.
-        log_subprocess(line)
-    try:
-        proc.wait()
-    finally:
-        if proc.stdout:
-            proc.stdout.close()
-        if proc.stderr:
-            proc.stderr.close()
-
-    proc_had_error = (
-        proc.returncode and proc.returncode not in extra_ok_returncodes
-    )
-    if proc_had_error:
-        if on_returncode == 'raise':
-            if not showing_subprocess and log_failed_cmd:
-                # Then the subprocess streams haven't been logged to the
-                # console yet.
-                msg = make_subprocess_output_error(
-                    cmd_args=cmd,
-                    cwd=cwd,
-                    lines=all_output,
-                    exit_status=proc.returncode,
-                )
-                subprocess_logger.error(msg)
-            exc_msg = (
-                'Command errored out with exit status {}: {} '
-                'Check the logs for full command output.'
-            ).format(proc.returncode, command_desc)
-            raise SubProcessError(exc_msg)
-        elif on_returncode == 'warn':
-            subprocess_logger.warning(
-                'Command "%s" had error code %s in %s',
-                command_desc,
-                proc.returncode,
-                cwd,
-            )
-        elif on_returncode == 'ignore':
-            pass
-        else:
-            raise ValueError('Invalid value: on_returncode={!r}'.format(
-                             on_returncode))
-    return ''.join(all_output)
-
-
 def find_path_to_setup_from_repo_root(location, repo_root):
     # type: (str, str) -> Optional[str]
     """
@@ -798,6 +673,9 @@ class VersionControl(object):
         cwd=None,  # type: Optional[str]
         on_returncode='raise',  # type: str
         extra_ok_returncodes=None,  # type: Optional[Iterable[int]]
+        command_desc=None,  # type: Optional[str]
+        extra_environ=None,  # type: Optional[Mapping[str, Any]]
+        spinner=None,  # type: Optional[SpinnerInterface]
         log_failed_cmd=True  # type: bool
     ):
         # type: (...) -> Text
@@ -811,6 +689,10 @@ class VersionControl(object):
             return call_subprocess(cmd, show_stdout, cwd,
                                    on_returncode=on_returncode,
                                    extra_ok_returncodes=extra_ok_returncodes,
+                                   command_desc=command_desc,
+                                   extra_environ=extra_environ,
+                                   unset_environ=cls.unset_environ,
+                                   spinner=spinner,
                                    log_failed_cmd=log_failed_cmd)
         except OSError as e:
             # errno.ENOENT = no such file or directory

From 8665a3e1e2c6d95802ff351eb66fa59e0939e820 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?St=C3=A9phane=20Bidoul?= <stephane.bidoul@gmail.com>
Date: Mon, 21 Dec 2020 13:05:16 +0100
Subject: [PATCH 4/9] Revert "Improve check for svn version string"

This reverts commit 1471897b84b43c467c753b5edebe636f835afc6a.
---
 src/pip/_internal/vcs/subversion.py | 15 ++-------------
 1 file changed, 2 insertions(+), 13 deletions(-)

diff --git a/src/pip/_internal/vcs/subversion.py b/src/pip/_internal/vcs/subversion.py
index 2575872a7..b84108efc 100644
--- a/src/pip/_internal/vcs/subversion.py
+++ b/src/pip/_internal/vcs/subversion.py
@@ -25,7 +25,7 @@ _svn_info_xml_url_re = re.compile(r'<url>(.*)</url>')
 
 
 if MYPY_CHECK_RUNNING:
-    from typing import Optional, Text, Tuple
+    from typing import Optional, Tuple
 
     from pip._internal.utils.misc import HiddenText
     from pip._internal.utils.subprocess import CommandArgs
@@ -218,18 +218,7 @@ class Subversion(VersionControl):
         #   svn, version 1.12.0-SlikSvn (SlikSvn/1.12.0)
         #      compiled May 28 2019, 13:44:56 on x86_64-microsoft-windows6.2
         version_prefix = 'svn, version '
-        cmd_output = self.run_command(['--version'], show_stdout=False)
-
-        # Split the output by newline, and find the first line where
-        # version_prefix is present
-        output_lines = cmd_output.split('\n')
-        version = ''  # type: Text
-
-        for line in output_lines:
-            if version_prefix in line:
-                version = line
-                break
-
+        version = self.run_command(['--version'], show_stdout=False)
         if not version.startswith(version_prefix):
             return ()
 

From 19039c27e99349ef627aef55280158baef557e0b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?St=C3=A9phane=20Bidoul?= <stephane.bidoul@gmail.com>
Date: Mon, 21 Dec 2020 15:07:48 +0100
Subject: [PATCH 5/9] Revert "Bubble up SubProcessError to basecommand._main"

This reverts commit e9f738a3daec91b131ae985e16809d47b1cfdaff.
---
 src/pip/_internal/cli/base_command.py | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/src/pip/_internal/cli/base_command.py b/src/pip/_internal/cli/base_command.py
index 7f05efb85..41e7dcf10 100644
--- a/src/pip/_internal/cli/base_command.py
+++ b/src/pip/_internal/cli/base_command.py
@@ -27,7 +27,6 @@ from pip._internal.exceptions import (
     InstallationError,
     NetworkConnectionError,
     PreviousBuildDirError,
-    SubProcessError,
     UninstallationError,
 )
 from pip._internal.utils.deprecation import deprecated
@@ -230,7 +229,7 @@ class Command(CommandContextMixIn):
 
             return PREVIOUS_BUILD_DIR_ERROR
         except (InstallationError, UninstallationError, BadCommand,
-                SubProcessError, NetworkConnectionError) as exc:
+                NetworkConnectionError) as exc:
             logger.critical(str(exc))
             logger.debug('Exception information:', exc_info=True)
 

From bcc412c44aa59b5dd217dcd5b741bf2efec0962c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?St=C3=A9phane=20Bidoul?= <stephane.bidoul@gmail.com>
Date: Mon, 21 Dec 2020 13:33:46 +0100
Subject: [PATCH 6/9] Additional revert of 7969

Revert additional changes that were made
after 7969 and depended on it.
---
 src/pip/_internal/vcs/git.py | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/src/pip/_internal/vcs/git.py b/src/pip/_internal/vcs/git.py
index a6d1396fc..de9c7f519 100644
--- a/src/pip/_internal/vcs/git.py
+++ b/src/pip/_internal/vcs/git.py
@@ -11,7 +11,7 @@ from pip._vendor.packaging.version import parse as parse_version
 from pip._vendor.six.moves.urllib import parse as urllib_parse
 from pip._vendor.six.moves.urllib import request as urllib_request
 
-from pip._internal.exceptions import BadCommand, InstallationError, SubProcessError
+from pip._internal.exceptions import BadCommand, InstallationError
 from pip._internal.utils.misc import display_path, hide_url
 from pip._internal.utils.subprocess import make_command
 from pip._internal.utils.temp_dir import TempDirectory
@@ -332,9 +332,11 @@ class Git(VersionControl):
         """
         try:
             cls.run_command(
-                ['rev-parse', '-q', '--verify', "sha^" + rev], cwd=location
+                ['rev-parse', '-q', '--verify', "sha^" + rev],
+                cwd=location,
+                log_failed_cmd=False,
             )
-        except SubProcessError:
+        except InstallationError:
             return False
         else:
             return True

From 139293b5e2541df764f7760f790f42cdb0d48621 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?St=C3=A9phane=20Bidoul?= <stephane.bidoul@gmail.com>
Date: Mon, 21 Dec 2020 14:39:50 +0100
Subject: [PATCH 7/9] add stdout_only to call_subprocess

---
 src/pip/_internal/utils/subprocess.py | 69 ++++++++++++++++++---------
 1 file changed, 47 insertions(+), 22 deletions(-)

diff --git a/src/pip/_internal/utils/subprocess.py b/src/pip/_internal/utils/subprocess.py
index 605e711e6..3c79c7289 100644
--- a/src/pip/_internal/utils/subprocess.py
+++ b/src/pip/_internal/utils/subprocess.py
@@ -118,7 +118,8 @@ def call_subprocess(
     extra_environ=None,  # type: Optional[Mapping[str, Any]]
     unset_environ=None,  # type: Optional[Iterable[str]]
     spinner=None,  # type: Optional[SpinnerInterface]
-    log_failed_cmd=True  # type: Optional[bool]
+    log_failed_cmd=True,  # type: Optional[bool]
+    stdout_only=False,  # type: Optional[bool]
 ):
     # type: (...) -> Text
     """
@@ -130,6 +131,9 @@ def call_subprocess(
       unset_environ: an iterable of environment variable names to unset
         prior to calling subprocess.Popen().
       log_failed_cmd: if false, failed commands are not logged, only raised.
+      stdout_only: if true, return only stdout, else return both. When true,
+        logging of both stdout and stderr occurs when the subprocess has
+        terminated, else logging occurs as subprocess output is produced.
     """
     if extra_ok_returncodes is None:
         extra_ok_returncodes = []
@@ -180,8 +184,11 @@ def call_subprocess(
         proc = subprocess.Popen(
             # Convert HiddenText objects to the underlying str.
             reveal_command_args(cmd),
-            stderr=subprocess.STDOUT, stdin=subprocess.PIPE,
-            stdout=subprocess.PIPE, cwd=cwd, env=env,
+            stdin=subprocess.PIPE,
+            stdout=subprocess.PIPE,
+            stderr=subprocess.STDOUT if not stdout_only else subprocess.PIPE,
+            cwd=cwd,
+            env=env,
         )
         assert proc.stdin
         assert proc.stdout
@@ -193,25 +200,43 @@ def call_subprocess(
             )
         raise
     all_output = []
-    while True:
-        # The "line" value is a unicode string in Python 2.
-        line = console_to_str(proc.stdout.readline())
-        if not line:
-            break
-        line = line.rstrip()
-        all_output.append(line + '\n')
+    if not stdout_only:
+        # In this mode, stdout and stderr are in the same pip.
+        while True:
+            # The "line" value is a unicode string in Python 2.
+            line = console_to_str(proc.stdout.readline())
+            if not line:
+                break
+            line = line.rstrip()
+            all_output.append(line + '\n')
+
+            # Show the line immediately.
+            log_subprocess(line)
+            # Update the spinner.
+            if use_spinner:
+                assert spinner
+                spinner.spin()
+        try:
+            proc.wait()
+        finally:
+            if proc.stdout:
+                proc.stdout.close()
+        output = ''.join(all_output)
+    else:
+        # In this mode, stdout and stderr are in different pipes.
+        # We must use the communicate which is the only safe way to read both.
+        out_bytes, err_bytes = proc.communicate()
+        # log line by line to preserve pip log indenting
+        out = console_to_str(out_bytes)
+        for out_line in out.splitlines():
+            log_subprocess(out_line)
+        all_output.append(out)
+        err = console_to_str(err_bytes)
+        for err_line in err.splitlines():
+            log_subprocess(err_line)
+        all_output.append(err)
+        output = out
 
-        # Show the line immediately.
-        log_subprocess(line)
-        # Update the spinner.
-        if use_spinner:
-            assert spinner
-            spinner.spin()
-    try:
-        proc.wait()
-    finally:
-        if proc.stdout:
-            proc.stdout.close()
     proc_had_error = (
         proc.returncode and proc.returncode not in extra_ok_returncodes
     )
@@ -250,7 +275,7 @@ def call_subprocess(
         else:
             raise ValueError('Invalid value: on_returncode={!r}'.format(
                              on_returncode))
-    return ''.join(all_output)
+    return output
 
 
 def runner_with_spinner_message(message):

From 74369e860e5b6d1ea6fed4144cb9b506287990ec Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?St=C3=A9phane=20Bidoul?= <stephane.bidoul@gmail.com>
Date: Mon, 21 Dec 2020 14:46:21 +0100
Subject: [PATCH 8/9] vcs: capture subprocess stdout only

---
 news/8876.bugfix.rst                    |  3 +++
 src/pip/_internal/utils/subprocess.py   | 10 +++----
 src/pip/_internal/vcs/bazaar.py         |  6 +++--
 src/pip/_internal/vcs/git.py            | 35 ++++++++++++++++++++-----
 src/pip/_internal/vcs/mercurial.py      | 19 +++++++++++---
 src/pip/_internal/vcs/subversion.py     |  5 +++-
 src/pip/_internal/vcs/versioncontrol.py |  6 +++--
 7 files changed, 63 insertions(+), 21 deletions(-)
 create mode 100644 news/8876.bugfix.rst

diff --git a/news/8876.bugfix.rst b/news/8876.bugfix.rst
new file mode 100644
index 000000000..98250dc97
--- /dev/null
+++ b/news/8876.bugfix.rst
@@ -0,0 +1,3 @@
+Fixed hanging VCS subprocess calls when the VCS outputs a large amount of data
+on stderr. Restored logging of VCS errors that was inadvertently removed in pip
+20.2.
diff --git a/src/pip/_internal/utils/subprocess.py b/src/pip/_internal/utils/subprocess.py
index 3c79c7289..a75bc6875 100644
--- a/src/pip/_internal/utils/subprocess.py
+++ b/src/pip/_internal/utils/subprocess.py
@@ -190,9 +190,6 @@ def call_subprocess(
             cwd=cwd,
             env=env,
         )
-        assert proc.stdin
-        assert proc.stdout
-        proc.stdin.close()
     except Exception as exc:
         if log_failed_cmd:
             subprocess_logger.critical(
@@ -201,7 +198,10 @@ def call_subprocess(
         raise
     all_output = []
     if not stdout_only:
-        # In this mode, stdout and stderr are in the same pip.
+        assert proc.stdout
+        assert proc.stdin
+        proc.stdin.close()
+        # In this mode, stdout and stderr are in the same pipe.
         while True:
             # The "line" value is a unicode string in Python 2.
             line = console_to_str(proc.stdout.readline())
@@ -224,7 +224,7 @@ def call_subprocess(
         output = ''.join(all_output)
     else:
         # In this mode, stdout and stderr are in different pipes.
-        # We must use the communicate which is the only safe way to read both.
+        # We must use communicate() which is the only safe way to read both.
         out_bytes, err_bytes = proc.communicate()
         # log line by line to preserve pip log indenting
         out = console_to_str(out_bytes)
diff --git a/src/pip/_internal/vcs/bazaar.py b/src/pip/_internal/vcs/bazaar.py
index efe524492..4a63d6faa 100644
--- a/src/pip/_internal/vcs/bazaar.py
+++ b/src/pip/_internal/vcs/bazaar.py
@@ -93,7 +93,9 @@ class Bazaar(VersionControl):
 
     @classmethod
     def get_remote_url(cls, location):
-        urls = cls.run_command(['info'], show_stdout=False, cwd=location)
+        urls = cls.run_command(
+            ['info'], show_stdout=False, stdout_only=True, cwd=location
+        )
         for line in urls.splitlines():
             line = line.strip()
             for x in ('checkout of branch: ',
@@ -108,7 +110,7 @@ class Bazaar(VersionControl):
     @classmethod
     def get_revision(cls, location):
         revision = cls.run_command(
-            ['revno'], show_stdout=False, cwd=location,
+            ['revno'], show_stdout=False, stdout_only=True, cwd=location,
         )
         return revision.splitlines()[-1]
 
diff --git a/src/pip/_internal/vcs/git.py b/src/pip/_internal/vcs/git.py
index de9c7f519..565961a06 100644
--- a/src/pip/_internal/vcs/git.py
+++ b/src/pip/_internal/vcs/git.py
@@ -79,7 +79,9 @@ class Git(VersionControl):
 
     def get_git_version(self):
         VERSION_PFX = 'git version '
-        version = self.run_command(['version'], show_stdout=False)
+        version = self.run_command(
+            ['version'], show_stdout=False, stdout_only=True
+        )
         if version.startswith(VERSION_PFX):
             version = version[len(VERSION_PFX):].split()[0]
         else:
@@ -102,7 +104,11 @@ class Git(VersionControl):
         # and to suppress the message to stderr.
         args = ['symbolic-ref', '-q', 'HEAD']
         output = cls.run_command(
-            args, extra_ok_returncodes=(1, ), show_stdout=False, cwd=location,
+            args,
+            extra_ok_returncodes=(1, ),
+            show_stdout=False,
+            stdout_only=True,
+            cwd=location,
         )
         ref = output.strip()
 
@@ -135,8 +141,13 @@ class Git(VersionControl):
           rev: the revision name.
         """
         # Pass rev to pre-filter the list.
-        output = cls.run_command(['show-ref', rev], cwd=dest,
-                                 show_stdout=False, on_returncode='ignore')
+        output = cls.run_command(
+            ['show-ref', rev],
+            cwd=dest,
+            show_stdout=False,
+            stdout_only=True,
+            on_returncode='ignore',
+        )
         refs = {}
         for line in output.strip().splitlines():
             try:
@@ -310,7 +321,10 @@ class Git(VersionControl):
         # exits with return code 1 if there are no matching lines.
         stdout = cls.run_command(
             ['config', '--get-regexp', r'remote\..*\.url'],
-            extra_ok_returncodes=(1, ), show_stdout=False, cwd=location,
+            extra_ok_returncodes=(1, ),
+            show_stdout=False,
+            stdout_only=True,
+            cwd=location,
         )
         remotes = stdout.splitlines()
         try:
@@ -346,7 +360,10 @@ class Git(VersionControl):
         if rev is None:
             rev = 'HEAD'
         current_rev = cls.run_command(
-            ['rev-parse', rev], show_stdout=False, cwd=location,
+            ['rev-parse', rev],
+            show_stdout=False,
+            stdout_only=True,
+            cwd=location,
         )
         return current_rev.strip()
 
@@ -359,7 +376,10 @@ class Git(VersionControl):
         # find the repo root
         git_dir = cls.run_command(
             ['rev-parse', '--git-dir'],
-            show_stdout=False, cwd=location).strip()
+            show_stdout=False,
+            stdout_only=True,
+            cwd=location,
+        ).strip()
         if not os.path.isabs(git_dir):
             git_dir = os.path.join(location, git_dir)
         repo_root = os.path.abspath(os.path.join(git_dir, '..'))
@@ -418,6 +438,7 @@ class Git(VersionControl):
                 ['rev-parse', '--show-toplevel'],
                 cwd=location,
                 show_stdout=False,
+                stdout_only=True,
                 on_returncode='raise',
                 log_failed_cmd=False,
             )
diff --git a/src/pip/_internal/vcs/mercurial.py b/src/pip/_internal/vcs/mercurial.py
index 75e903cc8..d2d145f62 100644
--- a/src/pip/_internal/vcs/mercurial.py
+++ b/src/pip/_internal/vcs/mercurial.py
@@ -92,7 +92,10 @@ class Mercurial(VersionControl):
     def get_remote_url(cls, location):
         url = cls.run_command(
             ['showconfig', 'paths.default'],
-            show_stdout=False, cwd=location).strip()
+            show_stdout=False,
+            stdout_only=True,
+            cwd=location,
+        ).strip()
         if cls._is_local_repository(url):
             url = path_to_url(url)
         return url.strip()
@@ -104,7 +107,10 @@ class Mercurial(VersionControl):
         """
         current_revision = cls.run_command(
             ['parents', '--template={rev}'],
-            show_stdout=False, cwd=location).strip()
+            show_stdout=False,
+            stdout_only=True,
+            cwd=location,
+        ).strip()
         return current_revision
 
     @classmethod
@@ -115,7 +121,10 @@ class Mercurial(VersionControl):
         """
         current_rev_hash = cls.run_command(
             ['parents', '--template={node}'],
-            show_stdout=False, cwd=location).strip()
+            show_stdout=False,
+            stdout_only=True,
+            cwd=location,
+        ).strip()
         return current_rev_hash
 
     @classmethod
@@ -131,7 +140,8 @@ class Mercurial(VersionControl):
         """
         # find the repo root
         repo_root = cls.run_command(
-            ['root'], show_stdout=False, cwd=location).strip()
+            ['root'], show_stdout=False, stdout_only=True, cwd=location
+        ).strip()
         if not os.path.isabs(repo_root):
             repo_root = os.path.abspath(os.path.join(location, repo_root))
         return find_path_to_setup_from_repo_root(location, repo_root)
@@ -146,6 +156,7 @@ class Mercurial(VersionControl):
                 ['root'],
                 cwd=location,
                 show_stdout=False,
+                stdout_only=True,
                 on_returncode='raise',
                 log_failed_cmd=False,
             )
diff --git a/src/pip/_internal/vcs/subversion.py b/src/pip/_internal/vcs/subversion.py
index b84108efc..701f41db4 100644
--- a/src/pip/_internal/vcs/subversion.py
+++ b/src/pip/_internal/vcs/subversion.py
@@ -167,6 +167,7 @@ class Subversion(VersionControl):
                 xml = cls.run_command(
                     ['info', '--xml', location],
                     show_stdout=False,
+                    stdout_only=True,
                 )
                 url = _svn_info_xml_url_re.search(xml).group(1)
                 revs = [
@@ -218,7 +219,9 @@ class Subversion(VersionControl):
         #   svn, version 1.12.0-SlikSvn (SlikSvn/1.12.0)
         #      compiled May 28 2019, 13:44:56 on x86_64-microsoft-windows6.2
         version_prefix = 'svn, version '
-        version = self.run_command(['--version'], show_stdout=False)
+        version = self.run_command(
+            ['--version'], show_stdout=False, stdout_only=True
+        )
         if not version.startswith(version_prefix):
             return ()
 
diff --git a/src/pip/_internal/vcs/versioncontrol.py b/src/pip/_internal/vcs/versioncontrol.py
index 1d9cb08fe..0e807a2fb 100644
--- a/src/pip/_internal/vcs/versioncontrol.py
+++ b/src/pip/_internal/vcs/versioncontrol.py
@@ -676,7 +676,8 @@ class VersionControl(object):
         command_desc=None,  # type: Optional[str]
         extra_environ=None,  # type: Optional[Mapping[str, Any]]
         spinner=None,  # type: Optional[SpinnerInterface]
-        log_failed_cmd=True  # type: bool
+        log_failed_cmd=True,  # type: bool
+        stdout_only=False,  # type: bool
     ):
         # type: (...) -> Text
         """
@@ -693,7 +694,8 @@ class VersionControl(object):
                                    extra_environ=extra_environ,
                                    unset_environ=cls.unset_environ,
                                    spinner=spinner,
-                                   log_failed_cmd=log_failed_cmd)
+                                   log_failed_cmd=log_failed_cmd,
+                                   stdout_only=stdout_only)
         except OSError as e:
             # errno.ENOENT = no such file or directory
             # In other words, the VCS executable isn't available

From 570a45ae711f7b86a99e3023207c4d263c57f908 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?St=C3=A9phane=20Bidoul?= <stephane.bidoul@gmail.com>
Date: Tue, 22 Dec 2020 00:16:42 +0100
Subject: [PATCH 9/9] Add test for call_subprocess stdout_only

---
 tests/unit/test_utils_subprocess.py | 30 +++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/tests/unit/test_utils_subprocess.py b/tests/unit/test_utils_subprocess.py
index b0de2bf57..47c890050 100644
--- a/tests/unit/test_utils_subprocess.py
+++ b/tests/unit/test_utils_subprocess.py
@@ -14,6 +14,7 @@ from pip._internal.utils.subprocess import (
     format_command_args,
     make_command,
     make_subprocess_output_error,
+    subprocess_logger,
 )
 
 
@@ -154,6 +155,35 @@ def test_make_subprocess_output_error__non_ascii_line():
     assert actual == expected, u'actual: {}'.format(actual)
 
 
+@pytest.mark.parametrize(
+    ('stdout_only', 'expected'),
+    [
+        (True, ("out\n", "out\r\n")),
+        (False, ("out\nerr\n", "out\r\nerr\r\n", "err\nout\n", "err\r\nout\r\n")),
+    ],
+)
+def test_call_subprocess_stdout_only(capfd, monkeypatch, stdout_only, expected):
+    log = []
+    monkeypatch.setattr(subprocess_logger, "debug", lambda *args: log.append(args[0]))
+    out = call_subprocess(
+        [
+            sys.executable,
+            "-c",
+            "import sys; "
+            "sys.stdout.write('out\\n'); "
+            "sys.stderr.write('err\\n')"
+        ],
+        stdout_only=stdout_only,
+    )
+    assert out in expected
+    captured = capfd.readouterr()
+    assert captured.err == ""
+    assert (
+        log == ["Running command %s", "out", "err"]
+        or log == ["Running command %s", "err", "out"]
+    )
+
+
 class FakeSpinner(SpinnerInterface):
 
     def __init__(self):