Created
February 27, 2015 16:05
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branch-alias subcommand for git
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#!/bin/bash | |
# git branch-alias | |
# Version 1.07 | |
# Author: Phil S. | |
# Creates branch aliases, so that you can refer to a long branch name | |
# by a convenient short alias. This is just a "do what I mean" wrapper | |
# around git symbolic-ref, but without the (considerable) risk of | |
# trashing a branch if you get your arguments wrong | |
# Examples: | |
# git branch-alias short some-overly-long-branch-name # creates alias | |
# git branch-alias short # creates alias for current branch | |
# git log short | |
# git checkout short | |
# git push origin short # pushes the branch, not the alias/reference | |
# git branch-alias --delete short | |
# Caveats: | |
# Although everything else I've tried works seamlessly, I note that | |
# git merge <alias> will cause the alias name to be mentioned in the | |
# commit message, rather than the real branch. It would be nicer if | |
# the branch name appeared. | |
# Compatibility: | |
# Developed with git version 1.7.12.4 | |
# Tested with git version 1.9.0 | |
# | |
# Related git changes between versions 1.7.12.4 and 1.9.0: | |
# | |
# 1.8.0.1 | |
# * A symbolic ref refs/heads/SYM was not correctly removed with "git | |
# branch -d SYM"; the command removed the ref pointed by SYM | |
# instead. | |
# | |
# 1.8.1 | |
# * "git symbolic-ref" learned the "-d $symref" option to delete the | |
# named symbolic ref, which is more intuitive way to spell it than | |
# "update-ref -d --no-deref $symref". | |
#cwd=$(git rev-parse --show-toplevel) | |
git=$(git rev-parse --git-dir) | |
if [ $? -ne 0 ]; then | |
exit 1 | |
fi | |
command=$(basename $0) | |
command="git ${command##git-}" | |
# Process command line options | |
# MRK note: I stripped out the long option support because OS X couldn't | |
# handle it | |
opts=$(getopt hd "$@") | |
if [ $? -eq 0 ]; then | |
eval set -- ${opts} | |
while true; do | |
case "$1" in | |
( -d ) delete=1; shift;; | |
( -h ) help=1; shift; break;; | |
( -- ) shift; break;; | |
esac | |
done | |
else | |
help=1 # getopt returned (and reported) an error. | |
fi | |
# Process non-option arguments | |
symref=$1 | |
branch=$2 | |
if [ -z "${symref}" ]; then | |
help=1 | |
fi | |
if [ -n "${help}" ]; then | |
echo "\ | |
Usage: | |
${command} <alias> [ <branch> ] | |
${command} [ --delete | -d ] <alias> | |
Creates a symbolic reference <alias> referring to <branch>. | |
<branch> defaults to the current checked-out branch. | |
This symbolic reference acts as an alias for <branch>, and can be | |
used in its place. More specifically, it WILL be dereferenced to | |
its target in nearly all situations, so for any given command you | |
should treat every usage of <alias> as if it were actually <branch>. | |
To safely delete a branch alias, use: | |
${command} --delete <alias> | |
WARNING: These symbolic references appear in your branch list as: | |
<alias> -> <branch> | |
and so you might be tempted to try to delete them like a branch: | |
git branch -d <alias> | |
However this can cause problems. In git versions prior to 1.8.0.1 | |
<alias> will be dereferenced and you will instead delete the | |
branch it refers to (git will allow this even if you currently | |
have that branch checked out), and the symbolic reference will | |
still remain (referencing a branch which is no longer available). | |
In later versions of git the <alias> will be deleted rather than | |
the branch; however git will still not check to see whether you | |
currently have <alias> checked out, and will not prevent you | |
from deleting it in that situation. This will leave your HEAD ref | |
in an invalid state. Using ${command} -d <alias> resolves this | |
situation by switching HEAD to <alias>'s target. | |
" | |
exit 0 | |
fi | |
# Use the current branch by default. | |
if [ -z "${branch}" ]; then | |
branch=$(git symbolic-ref -q HEAD) | |
if [ $? -ne 0 ]; then | |
echo "Could not establish current HEAD." >&2 | |
exit 1 | |
fi | |
fi | |
# We expect plain branch names, but also accept the fully-qualified | |
# (refs/heads/NAME) paths needed by git symbolic-ref; so strip that | |
# refs/heads/ prefix if it is specified. | |
branch=${branch##refs/heads/} | |
symref=${symref##refs/heads/} | |
# Deleting a symref. | |
if [ -n "${delete}" ]; then | |
if [ ! -f "${git}/refs/heads/${symref}" ]; then | |
echo "Symbolic reference refs/heads/${symref} does not exist." >&2 | |
exit 1 | |
fi | |
# Verify that it IS a symbolic reference | |
if ! git show-ref --verify --heads --quiet "refs/heads/${symref}"; then | |
echo "refs/heads/${symref} is not a valid reference." >&2 | |
exit 1 | |
fi | |
if ! git symbolic-ref "refs/heads/${symref}" >/dev/null; then | |
echo "Error validating refs/heads/${symref} as symbolic reference." >&2 | |
exit 1 | |
fi | |
# If we currently have <symref> checked out, deleting it is bad | |
# (as HEAD would no longer be a valid reference). I believe we do | |
# need to inspect the file here, as attempting to read the HEAD | |
# reference via git dereferences it to its target branch, and thus | |
# we are unable to distinguish between the branch and the symref. | |
if grep -q "^ref: refs/heads/${symref}\$" "${git}/HEAD"; then | |
echo "Cannot delete the currently checked out symbolic reference." | |
branch=$(git symbolic-ref -q HEAD) | |
if [ $? -ne 0 ]; then | |
echo "Could not establish current HEAD." >&2 | |
exit 1 | |
fi | |
echo "Switching HEAD to target branch ${branch}" | |
# By using git symbolic-ref HEAD to find the target ref | |
# and setting HEAD to that target, nothing really changes, | |
# but we can now delete the reference safely. | |
if ! git symbolic-ref HEAD "${branch}"; then | |
echo "Error updating HEAD from ${symref} to ${branch}" >&2 | |
echo "Aborting." >&2 | |
exit 1 | |
fi | |
fi | |
# Delete the reference. | |
# git 1.8.1+ provides: git symbolic-ref --delete <symref> | |
# but older versions do not include that option, so we use | |
# the backwards-compatible command. | |
echo "Deleting symbolic reference refs/heads/${symref}" | |
git update-ref -d --no-deref "refs/heads/${symref}" | |
exit $? | |
fi | |
# Creating a new symbolic reference. | |
# Error checking. git symbolic-ref doesn't really do any, and will | |
# happily mess up your branches; particularly if you get the arguments | |
# the wrong way around (treating it like ln -s is a really bad idea). | |
if [ ! -f "${git}/refs/heads/${branch}" ]; then | |
echo "${git}/refs/heads/${branch}" | |
echo "Target refs/heads/${branch} does not exist." >&2 | |
exit 1 | |
fi | |
if [ -f "${git}/refs/heads/${symref}" ]; then | |
target=$(git symbolic-ref "refs/heads/${symref}") | |
if [ $? -eq 0 ]; then | |
echo "Symbolic reference refs/heads/${symref} already exists:" >&2 | |
echo " ${symref} -> ${target##refs/heads/}" >&2 | |
echo "To remove it, use: ${command} --delete ${symref}" >&2 | |
else | |
echo "File refs/heads/${symref} already exists" >&2 | |
echo "(and is not a symbolic reference!)" >&2 | |
fi | |
exit 1 | |
fi | |
if git show-ref --verify --heads --quiet "refs/heads/${symref}"; then | |
# n.b. I'm pretty sure this is unreachable, given the previous block. | |
echo "refs/heads/${symref} is a valid reference without a file!?" >&2 | |
exit 1 | |
fi | |
# The parameters are good. | |
# Generate the reference and display the confirmed result. | |
if git symbolic-ref "refs/heads/${symref}" "refs/heads/${branch}"; then | |
target=$(git symbolic-ref "refs/heads/${symref}") | |
echo " ${symref} -> ${target##refs/heads/}" | |
else | |
echo "Failed to create branch alias." >&2 | |
exit 1 | |
fi |
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Hi, how/where would do I install this?