是否可以在Git中为一个分支添加别名？

请注意,git版本2.7.0 - 2.8.2(包括)中的一个错误导致"git branch"显示"alias - > alias"而不是"alias - > branch"用于分支别名.如果您受到该bug的影响,我建议升级到2.8.3或更高版本.

#!/bin/sh
# git branch-alias
# Author: Phil S.
# Version 1.13.1
version=1.13.1

# Creates branch aliases, so that you can refer to a long branch name
# by a convenient short alias.  This is particularly useful for branch
# names beginning with bug-tracker ID numbers (or similar), where the
# benefits of tab-completion are greatly reduced.

# This is mostly a "do what I mean" wrapper around "git symbolic-ref",
# with numerous safety measures included in order to eliminate the
# (otherwise considerable) risk of trashing a branch if you get your
# arguments wrong.

# Installation:
# Place this script somewhere in your PATH and name it "git-branch-alias"
# and you will be able to invoke it with "git branch-alias" as per the
# following examples.  If you have obtained the script from the git
# mailing list, please see the "Mailing list archives" note below.

# Examples:
# git branch-alias   # create alias
# git branch-alias  # create alias for current branch
# git branch # view branches and branch aliases
# git log 
# git checkout 
# git push origin  # pushes the branch, not the alias/reference
# git branch-alias -d  # delete an alias safely
# git branch-alias -h # help / usage details

# Caveats:
# Although everything else I've tried works seamlessly, I note that
# git merge  will cause the alias name to be mentioned in the
# commit message, rather than the name of the real branch.  It would
# be nicer if the branch name appeared.

# Compatibility:
# Originally developed with git version 1.7.12.4
# Also tested with git versions 1.9.0, 2.5.4, 2.6.6, 2.8.3
#
# Related git changes between versions 1.7.12.4 and 2.8.3:
# git v1.8.0.1
#  * A symbolic ref refs/heads/SYM was not correctly removed with "git
#    branch -d SYM"; the command removed the ref pointed by SYM
#    instead.
#
# git v1.8.1
#  * "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".
#
# git v2.6.5
#  * "git symbolic-ref" forgot to report a failure with its exit status.
#
#  I believe this is commit 3e4068ed90fd3c6f24303560113aae6dbb758699:
#  > symbolic-ref: propagate error code from create_symref()
#  > If create_symref() fails, git-symbolic-ref will still exit with
#  > code 0, and our caller has no idea that the command did nothing.
#  > This appears to have been broken since the beginning of time
#
#  As this affects symref creation only, the sole adverse effect here
#  would be an unintended message to the user if symref creation had
#  actually failed (but not even a misleading one, on account of our
#  reading the reference after its creation, and thus displaying an
#  error if it turned out to be invalid).
#
# git v2.8.3
#  * A change back in version 2.7 to "git branch" broke display of a
#    symbolic ref in a non-standard place in the refs/ hierarchy (we
#    expect symbolic refs to appear in refs/remotes/*/HEAD to point at
#    the primary branch the remote has, and as .git/HEAD to point at the
#    branch we locally checked out).
#
#  This caused "git branch" to display "ref -> ref" instead of "ref -> branch"
#  for branch aliases.  The functionality still works otherwise, but is not
#  nearly so convenient to work with when you cannot trivially see what each
#  alias points to.  This bug affected git versions 2.7.0 - 2.8.2 (inclusive).

# Change log:
# v1.13.1
# Change incorrect uses of git show-ref, introduced by v1.10 (including
# effective regression of v1.08), to use git symbolic-ref instead.
#
# v1.12:
# Fix the option handling for '--', and added it to the help text.
#
# v1.11:
# Minor tidy-ups.  Re-posted to git mailing list:
# https://www.mail-archive.com/git%40vger.kernel.org/msg161274.html
#
# v1.10:
# No longer dependent on refs existing as individual files, as they
# may be packed in .git/packed-refs.
#
# v1.09:
# POSIX-compatible option handling and output.
# Documented an issue with "git branch" in git versions 2.7.0 - 2.8.2.
#
# v1.08:
# Remove test git show-ref --verify --heads --quiet "refs/heads/${symref}"
# for asserting that the specified reference was valid before deleting a
# reference, as we need to permit the deletion of references to branches
# which have /already/ been deleted, and this test prevented that.
# n.b. We already had another validation test to fall back on, using
# git symbolic-ref "refs/heads/${symref}"
#
# v1.07:
# Minor tweaks.  Posted as feature-request to git mailing list:
# https://www.mail-archive.com/git%40vger.kernel.org/msg49171.html

# Mailing list archives:
# If you are reading this via the git mailing list archives at gmane.org
# then this code will probably be broken by an email obfuscation filter
# which automatically converts the symbol '@' to the string '  '.
# Specifically the shell positional parameter expansion "$@" is changed
# to "$  "), so don't try to use the version from gmane.  The copy
# of this message at http://www.mail-archive.com/git%40vger.kernel.org/
# should have the correct code.

command=$(basename $0)
if [ "${command##git-}" != "${command}" ]; then
    command="git ${command##git-}"
fi

# Print argument (and newline) to stdout or stderr.
stdout () {
    printf %s\\n "$1"
}
stderr () {
    printf %s\\n "$1" >&2
}

# Returns the supplied parameters suitably quoted for later evaluation.
quote () {
    for param; do
        printf %s "${param}Z" | sed "s/'/'\\\\''/g;1s/^/'/;\$s/Z\$/' /"
    done
}

# Process option parameters.
parameters=
while [ $# -gt 0 ]; do
    case "$1" in
        ( -- ) {
            shift
            parameters="${parameters}$(quote "$@")"
            break
        };;
        ( -v | --version ) version_help=1; shift;;
        ( -h | --help    ) help=1; shift;;
        ( -d | --delete  ) delete=1; shift;;
        ( -* ) {
            stdout "Invalid option: $1"
            stdout
            shorthelp=1
            shift
        };;
        ( * ) { # non-option parameter
            parameters="${parameters}$(quote "$1")"
            shift
        };;
    esac
done

# Process non-option parameters.
eval "set -- ${parameters}"
symref=$1
branch=$2

# If too few or too many parameters were supplied, display shorthelp.
if [ -z "${symref}" ] || [ -n "$3" ]; then
    shorthelp=1
fi

# If displaying the version, exit immediately.
if [ -n "${version_help}" ]; then
    stdout "${command} version ${version}"
    exit 0
fi

# Don't let short help override long help.
if [ -n "${help}" ]; then
    shorthelp=
fi

# Include the usage summary in both short and long help.
if [ -n "${help}" ] || [ -n "${shorthelp}" ]; then
    cat < []
${command} (-d | --delete) [--] 
${command} (-v | --version)

EOF
fi

# n.b. Calling "git branch-alias --help" causes git to look for
# a man page for "git-branch-alias", so we shouldn't advertise
# the long option (although we support it if the script is called
# by its real name, rather than via git).
if [ -n "${shorthelp}" ]; then
    cat < referring to .
 defaults to the current checked-out branch.

This symbolic reference acts as an alias for , 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  as if it were actually .

If either  or  begins with a hyphen, you can use the
'--' option to prevent subsequent arguments being treated as options.

To safely delete a branch alias, always use:
${command} -d 

WARNING: These symbolic references appear in your branch list as:
  -> 
and so you might be tempted to try to delete them like a branch:
 git branch -d 

However this can cause problems.  In git versions prior to 1.8.0.1
 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  will be deleted rather than
the branch; however git will still not check to see whether you
currently have  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  resolves
this situation by first switching HEAD to 's target branch
if HEAD was currently set to .

EOF
    exit 0
fi

# Confirm the CWD is within a git repository.
#cwd=$(git rev-parse --show-toplevel)
git=$(git rev-parse --git-dir)
if [ $? -ne 0 ]; then
    exit 1
fi

# Use the current branch by default.
if [ -z "${branch}" ]; then
    branch=$(git symbolic-ref -q HEAD)
    if [ $? -ne 0 ]; then
        stderr "Could not establish current HEAD."
        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 "${delete}" ]; then
    # Verify that it IS a symbolic reference.
    if ! git symbolic-ref "refs/heads/${symref}" >/dev/null; then
        stderr "Error validating refs/heads/${symref} as symbolic reference."
        exit 1
    fi

    # If we currently have  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 "^ref: refs/heads/${symref}\$" "${git}/HEAD" >/dev/null 2>&1; then
        stdout "Cannot delete the currently checked out symbolic reference."
        branch=$(git symbolic-ref -q HEAD)
        if [ $? -ne 0 ]; then
            stderr "Could not establish current HEAD."
            exit 1
        fi
        stdout "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
            stderr "Error updating HEAD from ${symref} to ${branch}"
            stderr "Aborting."
            exit 1
        fi
    fi

    # Delete the reference.
    # git 1.8.1+ provides: git symbolic-ref --delete 
    # but older versions do not include that option, so we use
    # the backwards-compatible command.
    stdout "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 ! git show-ref --verify --heads --quiet "refs/heads/${branch}"; then
    stderr "Target branch refs/heads/${branch} does not exist."
    exit 1
fi
if target=$(git symbolic-ref -q "refs/heads/${symref}"); then
    stderr "Symbolic reference refs/heads/${symref} already exists:"
    stderr "  ${symref} -> ${target##refs/heads/}"
    stderr "To delete it, use: ${command} -d ${symref}"
    exit 1
elif git show-ref --verify --heads --quiet "refs/heads/${symref}"; then
    stderr "Reference refs/heads/${symref} already exists"
    stderr "(and is not a symbolic reference!)"
    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}")
    stdout "  ${symref} -> ${target##refs/heads/}"
else
    stderr "Failed to create branch alias."
    exit 1
fi
# EOF