Git-enabling wrapper script for opendiff

opendiff

#!/bin/bash

tmpdir=/tmp/opendiff-repo

fetch () {
    case $1 in
     *:*)
        mkdir -p $tmpdir
        commit=${1%%:*}
        filename=$(git ls-files --full-name --with-tree $commit ${1#*:})
        hash=$(git rev-list -n1 --abbrev-commit $commit)
        case `git rev-parse --symbolic-full-name $commit`//$commit in
         refs/tags/*)   desc=${commit//\//_} ;;
         refs/*//HEAD)  desc=$hash ;;
         refs/*)        desc=${commit//\//_}@$hash ;;
         *)             desc=$hash ;;
        esac
        tmp=$tmpdir/$desc:${1##*[:/]}
        git show $commit:$filename > $tmp
        echo $tmp
        ;;
     *) if [ -e "$1" ]
        then
            echo $1
        else
            mkdir -p $tmpdir
            commit=$1
            tmp=$tmpdir/commit:${commit//\//_}
            git show --format=fuller $commit > $tmp
            echo $tmp
        fi
        ;;
    esac
}

if [ $# -eq 1 ]
then
    /usr/bin/opendiff $(fetch "HEAD:$1") "$1"
else
    /usr/bin/opendiff $(fetch "$1") $(fetch "$2")
fi

This can be used to compare current or different versions of a file or to compare two commits:

• opendiff FILE compares the file in the current HEAD commit with its current state on disk.
• opendiff COMMIT1:FILE COMMIT2:FILE compares the file in the specified commits — either prefix may be left off to compare the current file on disk, and different files can be compared if you really want to.
• opendiff COMMIT1 COMMIT2 compares two extant commits, useful when rebasing or cherry-picking, etc.