merge(3p/git): Merge git upstream at v2.26.2

third_party/git/Documentation/git-grep.txt

@@ -59,8 +59,8 @@ grep.extendedRegexp::
 	other than 'default'.
 
 grep.threads::
-	Number of grep worker threads to use.  If unset (or set to 0),
-	8 threads are used by default (for now).
+	Number of grep worker threads to use. If unset (or set to 0), Git will
+	use as many threads as the number of logical cores available.
 
 grep.fullName::
 	If set to true, enable `--full-name` option by default.
@@ -96,7 +96,8 @@ OPTIONS
 	Recursively search in each submodule that has been initialized and
 	checked out in the repository.  When used in combination with the
 	<tree> option the prefix of all submodule output will be the name of
-	the parent project's <tree> object.
+	the parent project's <tree> object. This option has no effect
+	if `--no-index` is given.
 
 -a::
 --text::
@@ -271,6 +272,23 @@ providing this option will cause it to die.
 
 -f <file>::
 	Read patterns from <file>, one per line.
++
+Passing the pattern via <file> allows for providing a search pattern
+containing a \0.
++
+Not all pattern types support patterns containing \0. Git will error
+out if a given pattern type can't support such a pattern. The
+`--perl-regexp` pattern type when compiled against the PCRE v2 backend
+has the widest support for these types of patterns.
++
+In versions of Git before 2.23.0 patterns containing \0 would be
+silently considered fixed. This was never documented, there were also
+odd and undocumented interactions between e.g. non-ASCII patterns
+containing \0 and `--ignore-case`.
++
+In future versions we may learn to support patterns containing \0 for
+more search backends, until then we'll die when the pattern type in
+question doesn't support them.
 
 -e::
 	The next parameter is the pattern. This option has to be
@@ -330,6 +348,17 @@ EXAMPLES
 `git grep solution -- :^Documentation`::
 	Looks for `solution`, excluding files in `Documentation`.
 
+NOTES ON THREADS
+----------------
+
+The `--threads` option (and the grep.threads configuration) will be ignored when
+`--open-files-in-pager` is used, forcing a single-threaded execution.
+
+When grepping the object store (with `--cached` or giving tree objects), running
+with multiple threads might perform slower than single threaded if `--textconv`
+is given and there're too many text conversions. So if you experience low
+performance in this case, it might be desirable to use `--threads=1`.
+
 GIT
 ---
 Part of the linkgit:git[1] suite