Merge branch 'po/doc-assume-unchanged'

Fixes long-standing misunderstanding of what assume-unchanged is
about.  Some text near what is removed by the bottom patch may also
have to be removed.

* po/doc-assume-unchanged:
  gitignore.txt: do not suggest assume-unchanged
  doc: make clear --assume-unchanged's user contract

Documentation/git-update-index.txt

@@ -82,20 +82,18 @@ OPTIONS
         Set the execute permissions on the updated files.
 
 --[no-]assume-unchanged::
-	When these flags are specified, the object names recorded
+	When this flag is specified, the object names recorded
-	for the paths are not updated.  Instead, these options
+	for the paths are not updated.  Instead, this option
-	set and unset the "assume unchanged" bit for the
+	sets/unsets the "assume unchanged" bit for the
-	paths.  When the "assume unchanged" bit is on, Git stops
+	paths.  When the "assume unchanged" bit is on, the user
-	checking the working tree files for possible
+	promises not to change the file and allows Git to assume
-	modifications, so you need to manually unset the bit to
+	that the working tree file matches what is recorded in
-	tell Git when you change the working tree file. This is
+	the index.  If you want to change the working tree file,
+	you need to unset the bit to tell Git.  This is
 	sometimes helpful when working with a big project on a
 	filesystem that has very slow lstat(2) system call
 	(e.g. cifs).
 +
-This option can be also used as a coarse file-level mechanism
-to ignore uncommitted changes in tracked files (akin to what
-`.gitignore` does for untracked files).
 Git will fail (gracefully) in case it needs to modify this file
 in the index e.g. when merging in a commit;
 thus, in case the assumed-untracked file is changed upstream,

Documentation/gitignore.txt

@@ -138,9 +138,6 @@ NOTES
 The purpose of gitignore files is to ensure that certain files
 not tracked by Git remain untracked.
 
-To ignore uncommitted changes in a file that is already tracked,
-use 'git update-index {litdd}assume-unchanged'.
-
 To stop tracking a file that is currently tracked, use
 'git rm --cached'.
 
@@ -203,7 +200,6 @@ everything within `foo/bar`):
 SEE ALSO
 --------
 linkgit:git-rm[1],
-linkgit:git-update-index[1],
 linkgit:gitrepository-layout[5],
 linkgit:git-check-ignore[1]