Sudhanshu Mishra - Fix branch hierarchies in git

Fix branch hierarchies in git

You use git, good on ya! You branched off of a branch that should've been left alone. How do you change the "parent" of the new branch?!

Published on Monday, September 18, 2017

Fix branch hierarchies in git

Problem

In git, you branched off of a branch that has a failed build. You fixed the build in the child branch, but your CI server (e.g. Atlassian Bamboo) sees the failed build on the parent branch as a blocker for you to be able to merge back to develop.

Git Structure

develop
  | -- bad-branch
         | -- good-branch
         
# We want to merge good-branch to develop

Solution

Summary: Re-parent good-branch to develop :-)

How-To

Inspired from this SO Thread

  1. Get the shell script from here
#!/bin/sh
# Copyright 2013 Google Inc.
# Written by Mark Lodato <lodato@google.com>.
# Distributed under the GNU General Public License, version 2.0.

OPTIONS_SPEC="\
git reparent [OPTIONS] ((-p <parent>)... | --no-parent)
Recommit HEAD with a new set of parents.
--
h,help          show the help
e,edit          edit the commit message in an editor first
keep-committer  do not rewrite committer name and date
m,message=      use the given message instead of that of HEAD
p,parent=!      new parent to use; may be given multiple times
no-parent!      create a parentless commit
q,quiet         be quiet; only report errors
reset*          default behavior
no-reset!       print the new object id instead of updating HEAD
"
SUBDIRECTORY_OK=Yes
. "$(git --exec-path)/git-sh-setup" || exit $?
require_clean_work_tree reparent "Please commit or stash them first."

# Location of the temporary message.
msg_file="$GIT_DIR/reparent-msg"

die_with_usage() {
echo "error: $1" >&2
usage
}

get_committer_ident_from_commit () {
encoding=$(git config i18n.commitencoding || echo UTF-8)
git show -s --pretty=raw --encoding="$encoding" "$1" -- |
parse_ident_from_commit committer COMMITTER
}

edit=
message=
keep_committer=
no_parent=
no_reset=
parent_flags=
quiet=
while [ $# -gt 0 ]; do
case "$1" in
-p)
[ $# -eq 0 ] && die_with_usage "-p requires an argument"
shift
parent_flags="$parent_flags$(git rev-parse --sq-quote -p "$1")"
;;
--no-parent)         no_parent=1 ;;
-e)                  edit=1 ;;
--no-edit)           edit= ;;
-m)                  message="$2"; shift ;;
--no-message)        message= ;;
--keep-committer)    keep_committer=1 ;;
--no-keep-committer) keep_committer= ;;
-q)                  quiet=-q ;;
--no-quiet)          quiet= ;;
--reset)             no_reset= ;;
--no-reset)          no_reset=1 ;;
--)          shift; break ;;
*)           die "internal error: unknown flag $1" ;;
esac
shift
done
[ $# -gt 0 ] && \
die_with_usage "no positional arguments expected"
[ -z "$no_parent" -a -z "$parent_flags" ] && \
die_with_usage "either -p or --no-parent is required"
[ -n "$no_parent" -a -n "$parent_flags" ] && \
die_with_usage "-p and --no-parent are mutually exclusive"

# Create the commit.
if [ -n "$message" ]; then
echo "$message" > "$msg_file"
else
git cat-file commit HEAD | sed "1,/^$/d" > "$msg_file"
fi
if [ -n "$edit" ]; then
# TODO: use the normal `git commit` comment stripping stuff
git_editor "$msg_file" || die "no editor configured"
[ -s "$msg_file" ] || die "aborting due to empty commit message"
fi
eval "$(get_author_ident_from_commit HEAD)"
export GIT_AUTHOR_NAME GIT_AUTHOR_EMAIL GIT_AUTHOR_DATE
if [ -n "$keep_committer" ]; then
eval "$(get_committer_ident_from_commit HEAD)"
export GIT_COMMITTER_NAME GIT_COMMITTER_EMAIL GIT_COMMITTER_DATE
fi
old_head="$(git rev-parse --short HEAD)" || exit $?
new_head="$(eval "git commit-tree HEAD: $parent_flags" '< "$msg_file"')" || \
exit $?
rm "$msg_file"

# Print out the commit if --no-reset; otherwise update HEAD.
if [ -n "$no_reset" ]; then
echo "$new_head"
else
set_reflog_action reparent
git reset $quiet "$new_head" || exit $?
new_abbrev="$(git rev-parse --short HEAD)" || exit $?
[ -z "$quiet" ] && echo "Moved HEAD to $new_abbrev (was $old_head)"
fi
  1. To convert to Unix Format: download dos2Unix from here
dos2unix filename.extension
  1. Now open git bash or Ubuntu terminal, and issue this command:
chmod +x git-reparent.sh
  1. To reparent good-branch to develop:
git-reparent.sh -p develop
# Force push, because we know what we're doing :-)
git push -f