Re: [PATCH 2/2] filter-branch: fail gracefully when a filter fails

[Johannes Schindelin <Johannes.Schindelin@gmx.de>]

Hi,

On Thu, 5 Jul 2007, Jeff King wrote:

> status=`((cmd1; echo $? >&3) | cmd2) 3>&1`

Cute.

This is the replacement patch, then (I guess there are still some nits to 
be had, so I did not redo the proper patch yet):

 git-filter-branch.sh |   43 ++++++++++++++++++++++++++++++++-----------
 1 files changed, 32 insertions(+), 11 deletions(-)

diff --git a/git-filter-branch.sh b/git-filter-branch.sh
old mode 100644
new mode 100755
index 6cf67df..f08288d
--- a/git-filter-branch.sh
+++ b/git-filter-branch.sh
@@ -28,6 +28,16 @@ map()
 	fi
 }
 
+# override die(): this version puts in an extra line break, so that
+# the progress is still visible
+
+die()
+{
+	echo \ >&2
+	echo "$*" >&2
+	exit 1
+}
+
 # When piped a commit, output a script to set the ident of either
 # "author" or "committer
 
@@ -181,23 +191,29 @@ while read commit parents; do
 	export GIT_COMMIT=$commit
 	git cat-file commit "$commit" >../commit
 
-	eval "$(set_ident AUTHOR <../commit)"
-	eval "$(set_ident COMMITTER <../commit)"
-	eval "$filter_env" < /dev/null
+	eval "$(set_ident AUTHOR <../commit)" ||
+		die "setting author failed for commit $commit"
+	eval "$(set_ident COMMITTER <../commit)" ||
+		die "setting committer failed for commit $commit"
+	eval "$filter_env" < /dev/null ||
+		die "env filter failed: $filter_env"
 
 	if [ "$filter_tree" ]; then
 		git checkout-index -f -u -a
 		# files that $commit removed are now still in the working tree;
 		# remove them, else they would be added again
 		git ls-files -z --others | xargs -0 rm -f
-		eval "$filter_tree" < /dev/null
+		eval "$filter_tree" < /dev/null ||
+			die "tree filter failed: $filter_tree"
+
 		git diff-index -r $commit | cut -f 2- | tr '\n' '\0' | \
 			xargs -0 git update-index --add --replace --remove
 		git ls-files -z --others | \
 			xargs -0 git update-index --add --replace --remove
 	fi
 
-	eval "$filter_index" < /dev/null
+	eval "$filter_index" < /dev/null ||
+		die "index filter failed: $filter_index"
 
 	parentstr=
 	for parent in $parents; do
@@ -206,13 +222,17 @@ while read commit parents; do
 		done
 	done
 	if [ "$filter_parent" ]; then
-		parentstr="$(echo "$parentstr" | eval "$filter_parent")"
+		parentstr="$(echo "$parentstr" | eval "$filter_parent")" ||
+				die "parent filter failed: $filter_parent"
 	fi
 
-	sed -e '1,/^$/d' <../commit | \
-		eval "$filter_msg" | \
-		sh -c "$filter_commit" "git commit-tree" $(git write-tree) \
-			$parentstr > ../map/$commit
+	(sed -e '1,/^$/d' <../commit |
+		(eval "$filter_msg" ||
+		 die "msg filter failed: $filter_msg" 2>&3) |
+		(sh -c "$filter_commit" "git commit-tree" $(git write-tree) \
+			$parentstr > ../map/$commit ||
+		 die "commit filter failed: $filter_commit" 2>&3)) 3>&1 |
+	 grep . && die
 done <../revs
 
 src_head=$(tail -n 1 ../revs | sed -e 's/ .*//')
@@ -249,7 +269,8 @@ if [ "$filter_tag_name" ]; then
 		[ -f "../map/$sha1" ] || continue
 		new_sha1="$(cat "../map/$sha1")"
 		export GIT_COMMIT="$sha1"
-		new_ref="$(echo "$ref" | eval "$filter_tag_name")"
+		new_ref="$(echo "$ref" | eval "$filter_tag_name")" ||
+			die "tag name filter failed: $filter_tag_name"
 
 		echo "$ref -> $new_ref ($sha1 -> $new_sha1)"