10: fix var-assigns before special builtins & fn calls in posix mode
11: fixed missing quoted nul removal (in one odd case).
See the patch files (once fetched) for more details of what was altered.
The patches fix:
1. Under certain circumstances, the glob expansion code did not remove
backslashes escaping characters in directory names (or portions of a
pattern preceding a slash).
2. When an alias value ends with an unquoted literal tab (not part of a quoted
string or comment), alias expansion cannot correctly detect the end of the
alias value after expanding it.
3. There are several incompatibilities in how bash-5.0 processes pathname
expansion (globbing) of filename arguments that have backslashes in the
directory portion.
4. In bash-5.0, the `wait' builtin without arguments waits for all children
of the shell. This includes children it `inherited' at shell invocation time.
This patch modifies the behavior to not wait for these inherited children,
some of which might be long-lived.
5. In certain cases, bash optimizes out a fork() call too early and prevents
traps from running.
6. Bash-5.0 did not build successfully if SYSLOG_HISTORY was defined without
also defining SYSLOG_SHOPT.
7. Running `exec' when job control was disabled, even temporarily, but after it
had been initialized, could leave the terminal in the wrong process group for
the executed process.
Changelog:
This is a terse description of the new features added to bash-5.0 since
the release of bash-4.4. As always, the manual page (doc/bash.1) is
the place to look for complete descriptions.
1. New Features in Bash
a. The `wait' builtin can now wait for the last process substitution created.
b. There is an EPOCHSECONDS variable, which expands to the time in seconds
since the Unix epoch.
c. There is an EPOCHREALTIME variable, which expands to the time in seconds
since the Unix epoch with microsecond granularity.
d. New loadable builtins: rm, stat, fdflags.
e. BASH_ARGV0: a new variable that expands to $0 and sets $0 on assignment.
f. When supplied a numeric argument, the shell-expand-line bindable readline
command does not perform quote removal and suppresses command and process
substitution.
g. `history -d' understands negative arguments: negative arguments offset from
the end of the history list.
h. The `name' argument to the `coproc' reserved word now undergoes word
expansion, so unique coprocs can be created in loops.
i. A nameref name resolution loop in a function now resolves to a variable by
that name in the global scope.
j. The `wait' builtin now has a `-f' option, which signfies to wait until the
specified job or process terminates, instead of waiting until it changes
state.
k. There is a define in config-top.h that allows the shell to use a static
value for $PATH, overriding whatever is in the environment at startup, for
use by the restricted shell.
l. Process substitution does not inherit the `v' option, like command
substitution.
m. If a non-interactive shell with job control enabled detects that a foreground
job died due to SIGINT, it acts as if it received the SIGINT.
n. The SIGCHLD trap is run once for each exiting child process even if job
control is not enabled when the shell is in Posix mode.
o. A new shopt option: localvar_inherit; if set, a local variable inherits the
value of a variable with the same name at the nearest preceding scope.
p. `bind -r' now checks whether a key sequence is bound before binding it to
NULL, to avoid creating keymaps for a multi-key sequence.
q. A numeric argument to the line editing `operate-and-get-next' command
specifies which history entry to use.
r. The positional parameters are now assigned before running the shell startup
files, so startup files can use $@.
s. There is a compile-time option that forces the shell to disable the check
for an inherited OLDPWD being a directory.
t. The `history' builtin can now delete ranges of history entries using
`-d start-end'.
u. The `vi-edit-and-execute-command' bindable readline command now puts readline
back in vi insertion mode after executing commands from the edited file.
v. The command completion code now matches aliases and shell function names
case-insensitively if the readline completion-ignore-case variable is set.
w. There is a new `assoc_expand_once' shell option that attempts to expand
associative array subscripts only once.
x. The shell only sets up BASH_ARGV and BASH_ARGC at startup if extended
debugging mode is active. The old behavior of unconditionally setting them
is available as part of the shell compatibility options.
y. The `umask' builtin now allows modes and masks greater than octal 777.
z. The `times' builtin now honors the current locale when printing a decimal
point.
aa. There is a new (disabled by default, undocumented) shell option to enable
and disable sending history to syslog at runtime.
bb. Bash no longer allows variable assignments preceding a special builtin that
changes variable attributes to propagate back to the calling environment
unless the compatibility level is 44 or lower.
cc. You can set the default value for $HISTSIZE at build time in config-top.h.
dd. The `complete' builtin now accepts a -I option that applies the completion
to the initial word on the line.
ee. The internal bash malloc now uses mmap (if available) to satisfy requests
greater than 128K bytes, so free can use mfree to return the pages to the
kernel.
ff. The shell doesn't automatically set BASH_ARGC and BASH_ARGV at startup
unless it's in debugging mode, as the documentation has always said, but
will dynamically create them if a script references them at the top level
without having enabled debugging mode.
gg. The localvar_inherit option will not attempt to inherit a value from a
variable of an incompatible type (indexed vs. associative arrays, for
example).
hh. The `globasciiranges' option is now enabled by default; it can be set to
off by default at configuration time.
ii. Associative and indexed arrays now allow subscripts consisting solely of
whitespace.
jj. `checkwinsize' is now enabled by default.
kk. The `localvar_unset' shopt option is now visible and documented.
ll. The `progcomp_alias' shopt option is now visible and documented.
mm. The signal name processing code now understands `SIGRTMIN+n' all the way
up to SIGRTMAX.
nn. There is a new `seq' loadable builtin.
oo. Trap execution now honors the (internal) max invocations of `eval', since
traps are supposed to be executed as if using `eval'.
pp. The $_ variable doesn't change when the shell executes a command that forks.
qq. The `kill' builtin now supports -sSIGNAME and -nSIGNUM, even though
conforming applications aren't supposed to use them.
rr. POSIX mode now enables the `shift_verbose' option.
2. New Features in Readline
a. Non-incremental vi-mode search (`N', `n') can search for a shell pattern, as
Posix specifies (uses fnmatch(3) if available).
b. There are new `next-screen-line' and `previous-screen-line' bindable
commands, which move the cursor to the same column in the next, or previous,
physical line, respectively.
c. There are default key bindings for control-arrow-key key combinations.
d. A negative argument (-N) to `quoted-insert' means to insert the next N
characters using quoted-insert.
e. New public function: rl_check_signals(), which allows applications to
respond to signals that readline catches while waiting for input using
a custom read function.
f. There is new support for conditionally testing the readline version in an
inputrc file, with a full set of arithmetic comparison operators available.
g. There is a simple variable comparison facility available for use within an
inputrc file. Allowable operators are equality and inequality; string
variables may be compared to a value; boolean variables must be compared to
either `on' or `off'; variable names are separated from the operator by
whitespace.
h. The history expansion library now understands command and process
substitution and extended globbing and allows them to appear anywhere in a
word.
i. The history library has a new variable that allows applications to set the
initial quoting state, so quoting state can be inherited from a previous
line.
j. Readline now allows application-defined keymap names; there is a new public
function, rl_set_keymap_name(), to do that.
k. The "Insert" keypad key, if available, now puts readline into overwrite
mode.
Changelog:
Bug-Description:
With certain values for PS1, especially those that wrap onto three or more
lines, readline will miscalculate the number of invisible characters,
leading to crashes and core dumps.
changes:
patch 06:
Out-of-range negative offsets to popd can cause the shell to crash attempting
to free an invalid memory block.
patch 07:
When performing filename completion, bash dequotes the directory name being
completed, which can result in match failures and potential unwanted
expansion.
patch 08:
Under certain circumstances, bash will evaluate arithmetic expressions as
part of reading an expression token even when evaluation is suppressed. This
happens while evaluating a conditional expression and skipping over the
failed branch of the expression.
patch 09:
Depending on compiler optimizations and behavior, the `read' builtin may not
save partial input when a timeout occurs.
patch 10:
Depending on compiler optimizations and behavior, the `read' builtin may not
save partial input when a timeout occurs.
patch 11:
Subshells begun to run command and process substitutions may attempt to
set the terminal's process group to an incorrect value if they receive
a fatal signal. This depends on the behavior of the process that starts
the shell.
MASTER_SITES= site1 \
site2
style continuation lines to be simple repeated
MASTER_SITES+= site1
MASTER_SITES+= site2
lines. As previewed on tech-pkg. With thanks to rillig for fixing pkglint
accordingly.
This is a terse description of the new features added to bash-4.4 since
the release of bash-4.3. As always, the manual page (doc/bash.1) is
the place to look for complete descriptions.
1. New Features in Bash
a. There is now a settable configuration #define that will cause the shell
to exit if the shell is running setuid without the -p option and setuid
to the real uid fails.
b. Command and process substitutions now turn off the `-v' option when
executing, as other shells seem to do.
c. The default value for the `checkhash' shell option may now be set at
compile time with a #define.
d. The `mapfile' builtin now has a -d option to use an arbitrary character
as the record delimiter, and a -t option to strip the delimiter as
supplied with -d.
e. The maximum number of nested recursive calls to `eval' is now settable in
config-top.h; the default is no limit.
f. The `-p' option to declare and similar builtins will display attributes for
named variables even when those variables have not been assigned values
(which are technically unset).
g. The maximum number of nested recursive calls to `source' is now settable
in config-top.h; the default is no limit.
h. All builtin commands recognize the `--help' option and print a usage
summary.
i. Bash does not allow function names containing `/' and `=' to be exported.
j. The `ulimit' builtin has new -k (kqueues) and -P (pseudoterminals) options.
k. The shell now allows `time ; othercommand' to time null commands.
l. There is a new `--enable-function-import' configuration option to allow
importing shell functions from the environment; import is enabled by
default.
m. `printf -v var ""' will now set `var' to the empty string, as if `var=""'
had been executed.
n. GLOBIGNORE, the pattern substitution word expansion, and programmable
completion match filtering now honor the value of the `nocasematch' option.
o. There is a new ${parameter@spec} family of operators to transform the
value of `parameter'.
p. Bash no longer attempts to perform compound assignment if a variable on the
rhs of an assignment statement argument to `declare' has the form of a
compound assignment (e.g., w='(word)' ; declare foo=$w); compound
assignments are accepted if the variable was already declared as an array,
but with a warning.
q. The declare builtin no longer displays array variables using the compound
assignment syntax with quotes; that will generate warnings when re-used as
input, and isn't necessary.
r. Executing the rhs of && and || will no longer cause the shell to fork if
it's not necessary.
s. The `local' builtin takes a new argument: `-', which will cause it to save
and the single-letter shell options and restore their previous values at
function return.
t. `complete' and `compgen' have a new `-o nosort' option, which forces
readline to not sort the completion matches.
u. Bash now allows waiting for the most recent process substitution, since it
appears as $!.
v. The `unset' builtin now unsets a scalar variable if it is subscripted with
a `0', analogous to the ${var[0]} expansion.
w. `set -i' is no longer valid, as in other shells.
x. BASH_SUBSHELL is now updated for process substitution and group commands
in pipelines, and is available with the same value when running any exit
trap.
y. Bash now checks $INSIDE_EMACS as well as $EMACS when deciding whether or
not bash is being run in a GNU Emacs shell window.
z. Bash now treats SIGINT received when running a non-builtin command in a
loop the way it has traditionally treated running a builtin command:
running any trap handler and breaking out of the loop.
aa. New variable: EXECIGNORE; a colon-separate list of patterns that will
cause matching filenames to be ignored when searching for commands.
bb. Aliases whose value ends in a shell metacharacter now expand in a way to
allow them to be `pasted' to the next token, which can potentially change
the meaning of a command (e.g., turning `&' into `&&').
cc. `make install' now installs the example loadable builtins and a set of
bash headers to use when developing new loadable builtins.
dd. `enable -f' now attempts to call functions named BUILTIN_builtin_load when
loading BUILTIN, and BUILTIN_builtin_unload when deleting it. This allows
loadable builtins to run initialization and cleanup code.
ee. There is a new BASH_LOADABLES_PATH variable containing a list of directories
where the `enable -f' command looks for shared objects containing loadable
builtins.
ff. The `complete_fullquote' option to `shopt' changes filename completion to
quote all shell metacharacters in filenames and directory names.
gg. The `kill' builtin now has a `-L' option, equivalent to `-l', for
compatibility with Linux standalone versions of kill.
hh. BASH_COMPAT and FUNCNEST can be inherited and set from the shell's initial
environment.
ii. inherit_errexit: a new `shopt' option that, when set, causes command
substitutions to inherit the -e option. By default, those subshells disable
-e. It's enabled as part of turning on posix mode.
jj. New prompt string: PS0. Expanded and displayed by interactive shells after
reading a complete command but before executing it.
kk. Interactive shells now behave as if SIGTSTP/SIGTTIN/SIGTTOU are set to
SIG_DFL when the shell is started, so they are set to SIG_DFL in child
processes.
ll. Posix-mode shells now allow double quotes to quote the history expansion
character.
mm. OLDPWD can be inherited from the environment if it names a directory.
nn. Shells running as root no longer inherit PS4 from the environment, closing
a security hole involving PS4 expansion performing command substitution.
oo. If executing an implicit `cd' when the `autocd' option is set, bash will
now invoke a function named `cd' if one exists before executing the `cd'
builtin.
pp. Value conversions (arithmetic expansions, case modification, etc.) now
happen when assigning elements of an array using compound assignment.
qq. There is a new option settable in config-top.h that makes multiple
directory arguments to `cd' a fatal error.
rr. Bash now uses mktemp() when creating internal temporary files; it produces
a warning at build time on many Linux systems.
2. New Features in Readline
a. The history truncation code now uses the same error recovery mechansim as
the history writing code, and restores the old version of the history file
on error. The error recovery mechanism handles symlinked history files.
b. There is a new bindable variable, `enable-bracketed-paste', which enables
support for a terminal's bracketed paste mode.
c. The editing mode indicators can now be strings and are user-settable
(new `emacs-mode-string', `vi-cmd-mode-string' and `vi-ins-mode-string'
variables). Mode strings can contain invisible character sequences.
Setting mode strings to null strings restores the defaults.
d. Prompt expansion adds the mode string to the last line of a multi-line
prompt (one with embedded newlines).
e. There is a new bindable variable, `colored-completion-prefix', which, if
set, causes the common prefix of a set of possible completions to be
displayed in color.
f. There is a new bindable command `vi-yank-pop', a vi-mode version of emacs-
mode yank-pop.
g. The redisplay code underwent several efficiency improvements for multibyte
locales.
h. The insert-char function attempts to batch-insert all pending typeahead
that maps to self-insert, as long as it is coming from the terminal.
i. rl_callback_sigcleanup: a new application function that can clean up and
unset any state set by readline's callback mode. Intended to be used
after a signal.
j. If an incremental search string has its last character removed with DEL, the
resulting empty search string no longer matches the previous line.
k. If readline reads a history file that begins with `#' (or the value of
the history comment character) and has enabled history timestamps, the
history entries are assumed to be delimited by timestamps. This allows
multi-line history entries.
l. Readline now throws an error if it parses a key binding without a
terminating `:' or whitespace.
m. The default binding for ^W in vi mode now uses word boundaries specified
by Posix (vi-unix-word-rubout is bindable command name).
n. rl_clear_visible_line: new application-callable function; clears all
screen lines occupied by the current visible readline line.
o. rl_tty_set_echoing: application-callable function that controls whether
or not readline thinks it is echoing terminal output.
p. Handle >| and strings of digits preceding and following redirection
specifications as single tokens when tokenizing the line for history
expansion.
q. Fixed a bug with displaying completions when the prefix display length
is greater than the length of the completions to be displayed.
r. The :p history modifier now applies to the entire line, so any expansion
specifying :p causes the line to be printed instead of expanded.
s. New application-callable function: rl_pending_signal(): returns the signal
number of any signal readline has caught but not yet handled.
t. New application-settable variable: rl_persistent_signal_handlers: if set
to a non-zero value, readline will enable the readline-6.2 signal handler
behavior in callback mode: handlers are installed when
rl_callback_handler_install is called and removed removed when a complete
line has been read.
Existing SHA1 digests verified, all found to be the same on the
machine holding the existing distfiles (morden). Existing SHA1
digests retained for now as an audit trail.
Fixes CVE-2014-6278:
A combination of nested command substitutions and function importing
from the environment can cause bash to execute code appearing in
the environment variable value following the function definition.
This is a terse description of the new features added to bash-4.3 since
the release of bash-4.2. As always, the manual page (doc/bash.1) is
the place to look for complete descriptions.
1. New Features in Bash
a. The `helptopic' completion action now maps to all the help topics, not just
the shell builtins.
b. The `help' builtin no longer does prefix substring matching first, so
`help read' does not match `readonly', but will do it if exact string
matching fails.
c. The shell can be compiled to not display a message about processes that
terminate due to SIGTERM.
d. Non-interactive shells now react to the setting of checkwinsize and set
LINES and COLUMNS after a foreground job exits.
e. There is a new shell option, `globasciiranges', which, when set to on,
forces globbing range comparisons to use character ordering as if they
were run in the C locale.
f. There is a new shell option, `direxpand', which makes filename completion
expand variables in directory names in the way bash-4.1 did.
g. In Posix mode, the `command' builtin does not change whether or not a
builtin it shadows is treated as an assignment builtin.
h. The `return' and `exit' builtins accept negative exit status arguments.
i. The word completion code checks whether or not a filename containing a
shell variable expands to a directory name and appends `/' to the word
as appropriate. The same code expands shell variables in command names
when performing command completion.
j. In Posix mode, it is now an error to attempt to define a shell function
with the same name as a Posix special builtin.
k. When compiled for strict Posix conformance, history expansion is disabled
by default.
l. The history expansion character (!) does not cause history expansion when
followed by the closing quote in a double-quoted string.
m. `complete' and its siblings compgen/compopt now takes a new `-o noquote'
option to inhibit quoting of the completions.
n. Setting HISTSIZE to a value less than zero causes the history list to be
unlimited (setting it 0 zero disables the history list).
o. Setting HISTFILESIZE to a value less than zero causes the history file size
to be unlimited (setting it to 0 causes the history file to be truncated
to zero size).
p. The `read' builtin now skips NUL bytes in the input.
q. There is a new `bind -X' option to print all key sequences bound to Unix
commands.
r. When in Posix mode, `read' is interruptible by a trapped signal. After
running the trap handler, read returns 128+signal and throws away any
partially-read input.
s. The command completion code skips whitespace and assignment statements
before looking for the command name word to be completed.
t. The build process has a new mechanism for constructing separate help files
that better reflects the current set of compilation options.
u. The -nt and -ot options to test now work with files with nanosecond
timestamp resolution.
v. The shell saves the command history in any shell for which history is
enabled and HISTFILE is set, not just interactive shells.
w. The shell has `nameref' variables and new -n(/+n) options to declare and
unset to use them, and a `test -R' option to test for them.
x. The shell now allows assigning, referencing, and unsetting elements of
indexed arrays using negative subscripts (a[-1]=2, echo ${a[-1]}) which
count back from the last element of the array.
y. The {x}<word redirection feature now allows words like {array[ind]} and
can use variables with special meanings to the shell (e.g., BASH_XTRACEFD).
z. There is a new CHILD_MAX special shell variable; its value controls the
number of exited child statues the shell remembers.
aa. There is a new configuration option (--enable-direxpand-default) that
causes the `direxpand' shell option to be enabled by default.
bb. Bash does not do anything special to ensure that the file descriptor
assigned to X in {x}<foo remains open after the block containing it
completes.
cc. The `wait' builtin has a new `-n' option to wait for the next child to
change status.
dd. The `printf' %(...)T format specifier now uses the current time if no
argument is supplied.
ee. There is a new variable, BASH_COMPAT, that controls the current shell
compatibility level.
ff. The `popd' builtin now treats additional arguments as errors.
gg. The brace expansion code now treats a failed sequence expansion as a
simple string and will continue to expand brace terms in the remainder
of the word.
hh. Shells started to run process substitutions now run any trap set on EXIT.
ii. The fc builtin now interprets -0 as the current command line.
jj. Completing directory names containing shell variables now adds a trailing
slash if the expanded result is a directory.
kk. `cd' has a new `-@' option to browse a file's extended attributes on
systems that support O_XATTR.
ll. The test/[/[[ `-v variable' binary operator now understands array
references.
2. New Features in Readline
a. Readline is now more responsive to SIGHUP and other fatal signals when
reading input from the terminal or performing word completion but no
longer attempts to run any not-allowable functions from a signal handler
context.
b. There are new bindable commands to search the history for the string of
characters between the beginning of the line and the point
(history-substring-search-forward, history-substring-search-backward)
c. Readline allows quoted strings as the values of variables when setting
them with `set'. As a side effect, trailing spaces and tabs are ignored
when setting a string variable's value.
d. The history library creates a backup of the history file when writing it
and restores the backup on a write error.
e. New application-settable variable: rl_filename_stat_hook: a function called
with a filename before using it in a call to stat(2). Bash uses it to
expand shell variables so things like $HOME/Downloads have a slash
appended.
f. New bindable function `print-last-kbd-macro', prints the most-recently-
defined keyboard macro in a reusable format.
g. New user-settable variable `colored-stats', enables use of colored text
to denote file types when displaying possible completions (colored analog
of visible-stats).
h. New user-settable variable `keyseq-timout', acts as an inter-character
timeout when reading input or incremental search strings.
i. New application-callable function: rl_clear_history. Clears the history list
and frees all readline-associated private data.
j. New user-settable variable, show-mode-in-prompt, adds a characters to the
beginning of the prompt indicating the current editing mode.
k. New application-settable variable: rl_input_available_hook; function to be
called when readline detects there is data available on its input file
descriptor.
l. Readline calls an application-set event hook (rl_event_hook) after it gets
a signal while reading input (read returns -1/EINTR but readline does not
handle the signal immediately) to allow the application to handle or
otherwise note it.
m. If the user-settable variable `history-size' is set to a value less than
0, the history list size is unlimited.
n. New application-settable variable: rl_signal_event_hook; function that is
called when readline is reading terminal input and read(2) is interrupted
by a signal. Currently not called for SIGHUP or SIGTERM.
o. rl_change_environment: new application-settable variable that controls
whether or not Readline modifies the environment (currently readline
modifies only LINES and COLUMNS).
are replaced with .include "../../devel/readline/buildlink3.mk", and
USE_GNU_READLINE are removed,
* .include "../../devel/readline/buildlink3.mk" without USE_GNU_READLINE
are replaced with .include "../../mk/readline.buildlink3.mk".
1. New Features in Bash
a. `exec -a foo' now sets $0 to `foo' in an executable shell script without a
leading #!.
b. Subshells begun to execute command substitutions or run shell functions or
builtins in subshells do not reset trap strings until a new trap is
specified. This allows $(trap) to display the caller's traps and the
trap strings to persist until a new trap is set.
c. `trap -p' will now show signals ignored at shell startup, though their
disposition still cannot be modified.
d. $'...', echo, and printf understand \uXXXX and \UXXXXXXXX escape sequences.
e. declare/typeset has a new `-g' option, which creates variables in the
global scope even when run in a shell function.
f. test/[/[[ have a new -v variable unary operator, which returns success if
`variable' has been set.
g. Posix parsing changes to allow `! time command' and multiple consecutive
instances of `!' (which toggle) and `time' (which have no cumulative
effect).
h. Posix change to allow `time' as a command by itself to print the elapsed
user, system, and real times for the shell and its children.
j. $((...)) is always parsed as an arithmetic expansion first, instead of as
a potential nested command substitution, as Posix requires.
k. A new FUNCNEST variable to allow the user to control the maximum shell
function nesting (recursive execution) level.
l. The mapfile builtin now supplies a third argument to the callback command:
the line about to be assigned to the supplied array index.
m. The printf builtin has a new %(fmt)T specifier, which allows time values
to use strftime-like formatting.
n. There is a new `compat41' shell option.
o. The cd builtin has a new Posix-mandated `-e' option.
p. Negative subscripts to indexed arrays, previously errors, now are treated
as offsets from the maximum assigned index + 1.
q. Negative length specifications in the ${var:offset:length} expansion,
previously errors, are now treated as offsets from the end of the variable.
r. Parsing change to allow `time -p --'.
s. Posix-mode parsing change to not recognize `time' as a keyword if the
following token begins with a `-'. This means no more Posix-mode
`time -p'. Posix interpretation 267.
t. There is a new `lastpipe' shell option that runs the last command of a
pipeline in the current shell context. The lastpipe option has no
effect if job control is enabled.
u. History expansion no longer expands the `$!' variable expansion.
v. Posix mode shells no longer exit if a variable assignment error occurs
with an assignment preceding a command that is not a special builtin.
w. Non-interactive mode shells exit if -u is enabled and an attempt is made
to use an unset variable with the % or # expansions, the `//', `^', or
`,' expansions, or the parameter length expansion.
x. Posix-mode shells use the argument passed to `.' as-is if a $PATH search
fails, effectively searching the current directory. Posix-2008 change.
2. New Features in Readline
a. The history library does not try to write the history filename in the
current directory if $HOME is unset. This closes a potential security
problem if the application does not specify a history filename.
b. New bindable variable `completion-display-width' to set the number of
columns used when displaying completions.
c. New bindable variable `completion-case-map' to cause case-insensitive
completion to treat `-' and `_' as identical.
d. There are new bindable vi-mode command names to avoid readline's case-
insensitive matching not allowing them to be bound separately.
e. New bindable variable `menu-complete-display-prefix' causes the menu
completion code to display the common prefix of the possible completions
before cycling through the list, instead of after.
