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

third_party/git/Documentation/git-clean.txt

@@ -26,18 +26,20 @@ are affected.
 OPTIONS
 -------
 -d::
-	Remove untracked directories in addition to untracked files.
-	If an untracked directory is managed by a different Git
-	repository, it is not removed by default.  Use -f option twice
-	if you really want to remove such a directory.
+	Normally, when no <path> is specified, git clean will not
+	recurse into untracked directories to avoid removing too much.
+	Specify -d to have it recurse into such directories as well.
+	If any paths are specified, -d is irrelevant; all untracked
+	files matching the specified paths (with exceptions for nested
+	git directories mentioned under `--force`) will be removed.
 
 -f::
 --force::
 	If the Git configuration variable clean.requireForce is not set
 	to false, 'git clean' will refuse to delete files or directories
-	unless given -f, -n or -i. Git will refuse to delete directories
-	with .git sub directory or file unless a second -f
-	is given.
+	unless given -f or -i.  Git will refuse to modify untracked
+	nested git repositories (directories with a .git subdirectory)
+	unless a second -f is given.
 
 -i::
 --interactive::