git am --rebasing clobbers commit encoding

From

NSNikolaus Schulz <microschulz@web.de>

Date

Mar 7, 2009, 16:38 UTC

Message-ID

<20090307163802.GA25501@luigi.zusammrottung.local>

Hi,

Here's the patch from 5e835cac:

diff --git a/git-am.sh b/git-am.sh
index 245e1db..5a7695e 100755
--- a/git-am.sh
+++ b/git-am.sh
@@ -327,11 +327,20 @@ do
 			echo "Patch is empty.  Was it split wrong?"
 			stop_here $this
 		}
-		SUBJECT="$(sed -n '/^Subject/ s/Subject: //p' "$dotest/info")"
-		case "$keep_subject" in -k)  SUBJECT="[PATCH] $SUBJECT" ;; esac
-
-		(echo "$SUBJECT" ; echo ; cat "$dotest/msg") |
-			git stripspace > "$dotest/msg-clean"
+		if test -f "$dotest/rebasing" &&
+			commit=$(sed -e 's/^From \([0-9a-f]*\) .*/\1/' \
+				-e q "$dotest/$msgnum") &&
+			test "$(git cat-file -t "$commit")" = commit
+		then
+			git cat-file commit "$commit" |
+			sed -e '1,/^$/d' >"$dotest/msg-clean"
+		else
+			SUBJECT="$(sed -n '/^Subject/ s/Subject: //p' "$dotest/info")"
+			case "$keep_subject" in -k)  SUBJECT="[PATCH] $SUBJECT" ;; esac
+
+			(echo "$SUBJECT" ; echo ; cat "$dotest/msg") |
+				git stripspace > "$dotest/msg-clean"
+		fi
 		;;
 	esac
 
The problem is, that "git cat-file commit .. | sed -e '1,/^$/d'"
discards the commit encoding header.  The commit message is taken as-is,
but later committed with the current i18n.commitEncoding.

I'm working on several machines, some of which use the legacy latin1
encoding; if I push a latin1-encoded commit to a machine using utf-8,
and rebase it there, the commits messages are corrupted.

This is particularly unlucky since with correct commit messages (no
multiple lines in first paragraph), "$dotest/msg" is perfectly fine, and
the above patch is not needed anyway.

Unfortunately, I don't see an easy way to fix this.  It seems to me that
recoding commit messages isn't really supported: commits are _always_
done with the configured i18n.commitencoding, and the only place where
recoding takes place is processing of patches sent by email, where
git-mailinfo recodes the commit message.  And commit 5e835cac has
bypassed git-mailinfo in git-am for rebasing.

I guess we cannot call iconv(1) after git cat-file because that's not
portable, and there is no plumbing command that can be used from a shell
script to convert the encoding of a commit; the functionality is in
utf8.c:reencode_string(), so only C code can use it.

Nikolaus