"git alias" command for adding/removing/editing git aliases conveniently

git-alias.sh

#!/bin/bash

set -eo pipefail

usage () {
    cat <<'EOF'
usage:
  git alias [<options>]
  git alias [<options>] name
  git alias [<options>] name newvalue
  git alias [<options>] -e|--edit name
  git alias [<options>] -d|--unset name

options:
  --system|--global|--local|--file <filename>

  When getting, the values are read from the system, global and repository local configuration files by default, and options --system, --global, --local and --file <filename> can be used to tell the command to read from only that location (see the section called “FILES” in "git config --help").

  When setting, the new value is written to the repository local configuration file by default, and options --system, --global, --file <filename> can be used to tell the command to write to that location (you can say --local but that is the default).

  When editing, the alias is read in the same way as "when getting" above, and the edited version is written back to the *same* repository as it was read from.

  When deleting, the alias is located in the same way as "when getting" above, and only the first match is deleted. Thus if you have overridden an alias "foo" in your local config, and you run "git alias -d foo" it will only remove the one from the local config and not from system nor global.
EOF

    exit 1
}

detect-origin () {
    case "$1" in
    	file:.git/config)
	    echo --local
	    ;;
	file:$HOME/.gitconfig)
	    echo --global
	    ;;
	file:/etc/gitconfig)
	    echo --system
	    ;;
	*)
	    echo "Unparseable origin '$1'" >&2
	    exit 3
	    ;;
    esac
}

while [ $# -gt 0 ]; do
    case "$1" in
	-h)
	    usage
	    ;;
	--system|--global|--local)
	    origin="$1"
	    shift
	    ;;
	-e|--edit)
	    shift
	    OP=edit
	    [ $# = 1 ] || usage
	    alias="$1"
	    ;;
	-d|--unset)
	    shift
	    OP=del
	    [ $# = 1 ] || usage
	    alias="$1"
	    ;;
	-*)
	    echo "Unsupported parameter: $1" >&2
	    usage
	    ;;
	*)
	    break
	    ;;
    esac
done

if [ ! "$OP" ]; then
    case $# in
	0)
	    OP=list
	    ;;
	1)
	    OP=get
	    alias="$1"
	    ;;
	2)
	    OP=set
	    alias="$1"
	    value="$2"
	    ;;
	*)
	    usage
	    ;;
    esac
fi

name="alias.$alias"

case "$OP" in
    list)
	git config $origin --list | perl -ne 'print if s/^alias\.//;'
	;;
    get)
	git config $origin --get "$name"
	;;
    set)
	git config $origin "$name" "$value"
	;;
    edit)
	file="$(mktemp "/tmp/git-alias-$alias-XXXXXXXX.sh")"
	git config $origin --show-origin --null --get "$name" | perl -e '<>=~m!(.*)\0(.*)\0! or die "lol"; print STDERR $1; print $2' > "$file" 2> "${file}.origin" || err=${PIPESTATUS[0]}
	case $err in
	    1)
		echo No ${origin#--} alias "'$alias'" >&2
		exit 1
		;;
	    "")
		:
		;;
	    *)
		echo "Error $err"
		exit $err
		;;
	esac
	origin="$(detect-origin "$(cat "${file}.origin")")"
	echo "Editing alias '$name' in ${origin#--}.."
	"$(git var GIT_EDITOR)" "$file"
	git config $origin "$name" "$(cat "$file")"
	echo "Updated alias '$name' in ${origin#--}"
	rm "$file" "${file}.origin"
	;;
    del)
	file="$(mktemp "/tmp/git-alias-$alias-XXXXXXXX.sh")"
	git config $origin --show-origin --null --get "$name" | perl -e '<>=~m!(.*)\0(.*)\0! or die "lol"; print STDERR $1; print $2' > "$file" 2> "${file}.origin" || err=${PIPESTATUS[0]}
	case $err in
	    1)
		echo No ${origin#--} alias "'$alias'" >&2
		exit 1
		;;
	    "")
		:
		;;
	    *)
		echo "Error $err"
		exit $err
		;;
	esac
	origin="$(detect-origin "$(cat "${file}.origin")")"
	rm "$file" "${file}.origin"
	git config $origin --unset "$name"
	echo "Deleted alias '$name' from ${origin#--}"
	;;
    *)
	echo "Internal error '$OP'" "$@" >&2
	exit 2
	;;
esac