revert(3p/git): Revert merge of git upstream at v2.26.2

This causes cgit to serve error pages, which is undesirable.

This reverts commit 5229c9b232, reversing
changes made to f2b211131f.

third_party/git/Documentation/git-add.txt

@@ -11,8 +11,7 @@ SYNOPSIS
 'git add' [--verbose | -v] [--dry-run | -n] [--force | -f] [--interactive | -i] [--patch | -p]
 	  [--edit | -e] [--[no-]all | --[no-]ignore-removal | [--update | -u]]
 	  [--intent-to-add | -N] [--refresh] [--ignore-errors] [--ignore-missing] [--renormalize]
-	  [--chmod=(+|-)x] [--pathspec-from-file=<file> [--pathspec-file-nul]]
-	  [--] [<pathspec>...]
+	  [--chmod=(+|-)x] [--] [<pathspec>...]
 
 DESCRIPTION
 -----------
@@ -188,19 +187,6 @@ for "git add --no-all <pathspec>...", i.e. ignored removed files.
 	bit is only changed in the index, the files on disk are left
 	unchanged.
 
---pathspec-from-file=<file>::
-	Pathspec is passed in `<file>` instead of commandline args. If
-	`<file>` is exactly `-` then standard input is used. Pathspec
-	elements are separated by LF or CR/LF. Pathspec elements can be
-	quoted as explained for the configuration variable `core.quotePath`
-	(see linkgit:git-config[1]). See also `--pathspec-file-nul` and
-	global `--literal-pathspecs`.
-
---pathspec-file-nul::
-	Only meaningful with `--pathspec-from-file`. Pathspec elements are
-	separated with NUL character and all other characters are taken
-	literally (including newlines and quotes).
-
 \--::
 	This option can be used to separate command-line options from
 	the list of files, (useful when filenames might be mistaken