Fix metadata hook script to support non-ascii characters

tips/automatically_adding_metadata/pre-commit-annex: Fix to not silently
skip filenames containing non-ascii characters.

git diff-index defaults to munging non-ascii characters. Using -z makes
it not do that, and then we just change the nulls to newlines.

This commit was sponsored by Jochen Bartl on Patreon.

CHANGELOG

@@ -28,6 +28,8 @@ git-annex (6.20180113) UNRELEASED; urgency=medium
     and the destination subdirectory does not exist yet.
   * Added annex.merge-annex-branches config setting which
     can be used to disable automatic merge of git-annex branches.
+  * tips/automatically_adding_metadata/pre-commit-annex: Fix to not
+    silently skip filenames containing non-ascii characters.
 
  -- Joey Hess <id@joeyh.name>  Wed, 24 Jan 2018 20:42:55 -0400
 

doc/bugs/automatically_adding_metadata_fails_on_files_with_UTF-8_umlauts.mdwn

@@ -65,3 +65,6 @@ ok
 ### Have you had any luck using git-annex before? (Sometimes we get tired of reading bug reports all day and a lil' positive end note does wonders)
 
 git annex is great. :)
+
+> [[fixed|done]]; caused by git diff-index defaulting to not emitting such
+> characters, got it to by using -z. --[[Joey]]

doc/tips/automatically_adding_metadata/pre-commit-annex

@@ -112,7 +112,7 @@ if [ -n "$*" ]; then
 		process "$f"
 	done
 else
-	git diff-index --name-only --cached $against | while read f; do
+	git diff-index -z --name-only --cached $against | sed 's/\x00/\n/g' | while read f; do
 		process "$f"
 	done
 fi