#!/bin/sh
# Copyright 2010 - 2012, Tim Henigan <tim.henigan@gmail.com>
#
# Perform a directory diff between commits in the repository using
# the external diff or merge tool specified in the user's config.

USAGE='[--cached] [--copy-back] [-x|--extcmd=<command>] <commit>{0,2} [-- <path>*]

    --cached     Compare to the index rather than the working tree.

    --copy-back  Copy files back to the working tree when the diff
                 tool exits (in case they were modified by the
                 user).  This option is only valid if the diff
                 compared with the working tree.

    -x=<command>
    --extcmd=<command>  Specify a custom command for viewing diffs.
                 git-diffall ignores the configured defaults and
                 runs $command $LOCAL $REMOTE when this option is
                 specified. Additionally, $BASE is set in the
                 environment.
'

SUBDIRECTORY_OK=1
. "$(git --exec-path)/git-sh-setup"

TOOL_MODE=diff
. "$(git --exec-path)/git-mergetool--lib"

merge_tool="$(get_merge_tool)"
if test -z "$merge_tool"
then
        echo "Error: Either the 'diff.tool' or 'merge.tool' option must be set."
        usage
fi

start_dir=$(pwd)

# All the file paths returned by the diff command are relative to the root
# of the working copy. So if the script is called from a subdirectory, it
# must switch to the root of working copy before trying to use those paths.
cdup=$(git rev-parse --show-cdup) &&
cd "$cdup" || {
        echo >&2 "Cannot chdir to $cdup, the toplevel of the working tree"
        exit 1
}

# set up temp dir
tmp=$(perl -e 'use File::Temp qw(tempdir);
        $t=tempdir("/tmp/git-diffall.XXXXX") or exit(1);
        print $t') || exit 1
trap 'rm -rf "$tmp" 2>/dev/null' EXIT

left=
right=
paths=
dashdash_seen=
compare_staged=
merge_base=
left_dir=
right_dir=
diff_tool=
copy_back=

while test $# != 0
do
        case "$1" in
        -h|--h|--he|--hel|--help)
                usage
                ;;
        --cached)
                compare_staged=1
                ;;
        --copy-back)
                copy_back=1
                ;;
        -x|--e|--ex|--ext|--extc|--extcm|--extcmd)
                if test $# = 1
                then
                        echo You must specify the tool for use with --extcmd
                        usage
                else
                        diff_tool=$2
                        shift
                fi
                ;;
        --)
                dashdash_seen=1
                ;;
        -*)
                echo Invalid option: "$1"
                usage
                ;;
        *)
                # could be commit, commit range or path limiter
                case "$1" in
                *...*)
                        left=${1%...*}
                        right=${1#*...}
                        merge_base=1
                        ;;
                *..*)
                        left=${1%..*}
                        right=${1#*..}
                        ;;
                *)
                        if test -n "$dashdash_seen"
                        then
                                paths="$paths$1 "
                        elif test -z "$left"
                        then
                                left=$1
                        elif test -z "$right"
                        then
                                right=$1
                        else
                                paths="$paths$1 "
                        fi
                        ;;
                esac
                ;;
        esac
        shift
done

# Determine the set of files which changed
if test -n "$left" && test -n "$right"
then
        left_dir="cmt-$(git rev-parse --short $left)"
        right_dir="cmt-$(git rev-parse --short $right)"

        if test -n "$compare_staged"
        then
                usage
        elif test -n "$merge_base"
        then
                git diff --name-only "$left"..."$right" -- $paths >"$tmp/filelist"
        else
                git diff --name-only "$left" "$right" -- $paths >"$tmp/filelist"
        fi
elif test -n "$left"
then
        left_dir="cmt-$(git rev-parse --short $left)"

        if test -n "$compare_staged"
        then
                right_dir="staged"
                git diff --name-only --cached "$left" -- $paths >"$tmp/filelist"
        else
                right_dir="working_tree"
                git diff --name-only "$left" -- $paths >"$tmp/filelist"
        fi
else
        left_dir="HEAD"

        if test -n "$compare_staged"
        then
                right_dir="staged"
                git diff --name-only --cached -- $paths >"$tmp/filelist"
        else
                right_dir="working_tree"
                git diff --name-only -- $paths >"$tmp/filelist"
        fi
fi

# Exit immediately if there are no diffs
if test ! -s "$tmp/filelist"
then
        exit 0
fi

if test -n "$copy_back" && test "$right_dir" != "working_tree"
then
        echo "--copy-back is only valid when diff includes the working tree."
        exit 1
fi

# Create the named tmp directories that will hold the files to be compared
mkdir -p "$tmp/$left_dir" "$tmp/$right_dir"

# Populate the tmp/right_dir directory with the files to be compared
if test -n "$right"
then
        while read name
        do
                ls_list=$(git ls-tree $right "$name")
                if test -n "$ls_list"
                then
                        mkdir -p "$tmp/$right_dir/$(dirname "$name")"
                        git show "$right":"$name" >"$tmp/$right_dir/$name" || true
                fi
        done < "$tmp/filelist"
elif test -n "$compare_staged"
then
        while read name
        do
                ls_list=$(git ls-files -- "$name")
                if test -n "$ls_list"
                then
                        mkdir -p "$tmp/$right_dir/$(dirname "$name")"
                        git show :"$name" >"$tmp/$right_dir/$name"
                fi
        done < "$tmp/filelist"
else
        while read name
        do
                if test -e "$name"
                then
                        mkdir -p "$tmp/$right_dir/$(dirname "$name")"
                        cp "$name" "$tmp/$right_dir/$name"
                fi
        done < "$tmp/filelist"
fi

# Populate the tmp/left_dir directory with the files to be compared
while read name
do
        if test -n "$left"
        then
                ls_list=$(git ls-tree $left "$name")
                if test -n "$ls_list"
                then
                        mkdir -p "$tmp/$left_dir/$(dirname "$name")"
                        git show "$left":"$name" >"$tmp/$left_dir/$name" || true
                fi
        else
                if test -n "$compare_staged"
                then
                        ls_list=$(git ls-tree HEAD "$name")
                        if test -n "$ls_list"
                        then
                                mkdir -p "$tmp/$left_dir/$(dirname "$name")"
                                git show HEAD:"$name" >"$tmp/$left_dir/$name"
                        fi
                else
                        mkdir -p "$tmp/$left_dir/$(dirname "$name")"
                        git show :"$name" >"$tmp/$left_dir/$name"
                fi
        fi
done < "$tmp/filelist"

cd "$tmp"
LOCAL="$left_dir"
REMOTE="$right_dir"

if test -n "$diff_tool"
then
        export BASE
        eval $diff_tool '"$LOCAL"' '"$REMOTE"'
else
        run_merge_tool "$merge_tool" false
fi

# Copy files back to the working dir, if requested
if test -n "$copy_back" && test "$right_dir" = "working_tree"
then
        cd "$start_dir"
        git_top_dir=$(git rev-parse --show-toplevel)
        find "$tmp/$right_dir" -type f |
        while read file
        do
                cp "$file" "$git_top_dir/${file#$tmp/$right_dir/}"
        done
fi