git-amend: My program to mimic darcs amend-record with git

From 2010. Needs fixing with recent Git. And better be upstreamed

http://git.vger.kernel.narkive.com/SoHylGJE/rfc-patch-git-amend-darcs-like-amend-record-for-git

bin/git-amend

+#!/bin/sh -e
+# git-amend: darcs like amend-record for git
+# FIXME error handling
+# TODO don't noise reflog
+
+USAGE="<commit>"
+SUBDIRECTORY_OK=Yes
+. git-sh-setup
+
+test "$#" = 1 || usage
+
+commit=$1
+
+# let's see if $commit is a valid one, and also transform it to sha1 for it not
+# to be dependant on current HEAD
+commit=$(git rev-parse "$commit")
+
+# look out merges!
+test -z "$(git log --merges ${commit}~..HEAD)" || \
+	die "E: can't amend commits behind merges"
+
+# commit index, allowing empty commit just for being able to amend patch
+# description
+git commit --allow-empty -m "amend for $commit"
+
+# save worktree/index state
+work=$(git stash create)
+test -n "$work" && git update-ref HEAD.amend-backup $work
+
+# reset to clean work/index before going into rebase
+git reset --hard HEAD
+
+fixup_cmd=$(mktemp -t git-amend-fixupcmd.XXXXXX)
+rest_cmd=$(mktemp -t git-amend-restcmd.XXXXXX)
+trap 'rm -f "$fixup_cmd" "$rest_cmd"' 0
+{
+echo -ne "pick\t";  git log --pretty=oneline -1 ${commit}
+echo -ne "fixup\t"; git log --pretty=oneline -1 ${HEAD}
+} > "$fixup_cmd"
+
+git log --pretty=oneline --reverse ${commit}..HEAD~ | awk '{print "pick\t" $0;}' \
+	> "$rest_cmd"
+
+# now let's apply fixup part to commit
+GIT_EDITOR="cat $fixup_cmd >" git rebase -i ${commit}~
+
+# reword it
+git commit -v --amend
+
+# and apply rest
+GIT_EDITOR="cat $rest_cmd >" git rebase -i HEAD
+
+# TODO verify that we ended up at the same tree we started
+
+# restore worktree/index state
+test -n "$work" && git stash apply --index $work