Yet Another Shell

makesignum: Use default for 0

The switch statement should be exhaustive to suppress compiler warning.

Pass values of correct type to printf

Makefile: Support zstd-compressed distribution

completion/git: Parse option arguments before target word

Amend parameter name in parse_cmdsubst_in_backquote

The parameter is about backslash-escaped double-quotes, not backquotes.
This commit fixes the parameter name and the doc comment.

doc/ja/params: Typo

Detect Vim more safely (#41000)

Makefile.in: Clear $MAKEFLAGS in distcheck

The "make check dist" command may execute a make different from the
currently executing make. The $MAKEFLAGS value should not be passed to
the different make implementation.

makedeps.yash: Return non-zero exit status on failure

Use configured CC in makedeps.yash (#41064)

share/initialization/common: work around user-defined cd (#41063)

Version 2.51

Up version to 2.51

Regex-specific escaping (#39094)

Don't quote ordinary characters in regex (#39094)

More test on bracket pattern in [[ ]]

test: quote_removal_and_regex_matching

This commit removes the `escaping' parameter from the
`quote_removal_and_test_triple' function in favor of the new
`quote_removal_and_regex_matching' function.

Test regex in [[ ]] portably

Allow parentheses and vertical bars in regex (#39094, #39449)

More tests on =~ in double bracket

More tests on failing brace expansions

Faster numeric brace expansion

In the previous numeric brace expansion algorithm, search for a dot
might scan the entire remainder of the string if there was no dot, which
unnecessarily took time before the expansion fails.

After this commit, we avoid scanning and only check the character that
needs to be checked.

Faster wglob (#40749)

More test on extended glob

Always nullify stdin in async list (#40903)

More test on stdin of asynchronous list

Documentation (#39287, #40842)

Run redirections w/o command name in subshell (#39287, #40842)

Assign before redirect in command w/o word (#39287, 40842)

Split exec_simple_command

Into the new two functions.