Using kdiff3 with subversion

This is the third and final installment of my ground-breaking and emotionally-charged story of how to use kdiff3 as your graphical differ with other tools.  And I've saved the best for last.  Which isn't saying much.

Subversion proved to be a thorny little bugger when it came to coaxing it into (successfully) using another graphical diff tool.  The reason being that it doesn't adhere to what can only generously be described as the 'standard' command-line arguments for diff tools.  And thus, in contrast to bzr (which merely needed a gesture in the direction of kdiff3), subversion requires a dedicated shell script to convert its command-line arguments into a form compatible with kdiff3.

But first, a few configuration changes in your ~/.subversion/config file:

[helpers]
diff-cmd = /home/<username>/.subversion/svndiffwrapper.sh
diff3-cmd = /home/<username>/.subversion/svndiffwrapper.sh
merge-tool-cmd = /home/<username>/.subversion/svndiffwrapper.sh

Note that there are existing comments in the config file associated with all but the last keyword, but I've omitted them for clarity.

'svndiffwrapper.sh' is the shell script that we'll describe in a moment.

Replace <username> with the username of the login that you use.  And yes, it really does need to be an absolute path reference ('~/<username>/...' won't work).  You don't have to put the script in your .subversion directory; you could use a shared location, as long as it's accessible by your user account (and any others that you wish to similarly configure).

See the rest of this post for the contents of the shell script.

Below is the shell script used as 'svndiffwrapper.sh' in the svn configuration.  Be sure that you 'chmod u+x' it so that svn can actually invoke it when needed (or 'chmod o+rx' if you put it someplace where you intend to share it among multiple users).

Note that I didn't write this script.  I discovered it somewhere when I was investigating how to get svn to use alternative graphical diff tools.  Unfortunately, I don't recall where I found it, or I'd be happy to provide a link and credits.  But it was made freely available, and I'm sure if you're inclined you can suss it out via google.  I don't recall whether or not I had to tweak it to get it to work with kdiff3, but it's possible.

Anyway, enjoy kdiff3 goodness when doing diffs and merges with subversion!

#!/bin/bash

# Return an errorcode of 0 on successful merge, 1 if unresolved conflicts
# remain in the result.  Any other errorcode will be treated as fatal.
# Author: Michael Bradley

# NOTE: all output must be redirected to stderr with "1>&2" as all stdout
# output is written to the output file

VDIFF3="kdiff3"
DIFF3="diff3"
DIFF="kdiff3"

promptUser ()
{
    read answer
    case "${answer}" in

        "M"         )
        echo "" 1>&2
        echo "Attempting to merge ${baseFileName} with ${DIFF}" 1>&2
        $VDIFF3 $older $mine $theirs --L1 $labelOlder --L2 $labelMine --L3 $labelTheirs -o $output 1>&2
        bLoop=1
        if [ -f $output ]; then
            if [ -s $output ]; then
                #output succesfully written
                bLoop=0
            fi
        fi
        if [ $bLoop = 0 ]; then
            cat $output
            rm -f $output
            exit 0
        else
            echo "Merge failed, try again" 1>&2
        fi

        ;;

        "m"         )
        echo "" 1>&2
        echo "Attempting to auto-merge ${baseFileName}" 1>&2
        diff3 -L $labelMine -L $labelOlder -L $labelTheirs -Em $mine $older $theirs > $output
        if [ $? = 1 ]; then
            #Can't auto merge
            rm -f $output
            $VDIFF3 $older $mine $theirs --L1 $labelOlder --L2 $labelMine --L3 $labelTheirs -o $output --auto 1>&2
            bLoop=1
            if [ -f $output ]; then
                if [ -s $output ]; then
                    #output succesfully written
                    bLoop=0
                fi
            fi
            if [ $bLoop = 0 ]; then
                cat $output
                rm -f $output
                exit 0
            else
                echo "Merge failed, try again" 1>&2
            fi
        else
            #We can automerge, and we already did it
            cat $output
            rm -f $output
            exit 0
        fi
        ;;

        "diff3" | "Diff3" | "DIFF3"  )
        echo "" 1>&2
        echo "Diffing..." 1>&2
        $VDIFF3 $older $mine $theirs --L1 $labelOlder --L2 $labelMine --L3 $labelTheirs 1>&2
        ;;

        "diff" | "Diff" | "DIFF"  )
        echo "" 1>&2
        echo "Diffing..." 1>&2
        $DIFF $mine $theirs -L $labelMine -L $labelTheirs 1>&2
        ;;

        "A" | "a"   ) 
        echo "" 1>&2
        echo "Accepting remote version of file..." 1>&2
        cat ${theirs}
        exit 0
        ;;

        "I" | "i"   ) 
        echo "" 1>&2
        echo "Keeping local modifications..." 1>&2
        cat ${mine}
        exit 0
        ;;

        "R" | "r"   ) 
        echo "" 1>&2
        echo "Reverting to base..." 1>&2
        cat ${older}
        exit 0
        ;;

        "D" | "d"   ) 
        echo "" 1>&2
        echo "Runnig diff3..." 1>&2
        diff3 -L $labelMine -L $labelOlder -L $labelTheirs -Em $mine $older $theirs
        #Exit with return vaule of the diff3 (to write out files if necessary)
        exit $?
        ;;

        "S" | "s"   ) 
        echo "" 1>&2
        echo "Saving for later..." 1>&2
        cat ${mine}
        #Exit with return vaule of 1 to force writting of files
        exit 1
        ;;

        "Fail" | "fail" | "FAIL"   ) 
        echo "" 1>&2
        echo "Failing..." 1>&2 
        exit 2
        ;;

        "H" | "h"   ) 
        echo "" 1>&2
        echo "USAGE OPTIONS:" 1>&2 
        echo "  [A]ccept    Accept $labelTheirs and throw out local modifications" 1>&2
        echo "  [D]efault   Use diff3 to merge files (same behavior as vanilla SVN)" 1>&2
        echo "  [Fail]      Kills the command (not suggested)" 1>&2
        echo "  [H]elp      Print this message" 1>&2
        echo "  [I]gnore    Keep your locally modified version as is" 1>&2
        echo "  [M]erge     Manually merge using ${VDIFF3}" 1>&2
        echo "  [m]erge     Same as "M" but attempts to automerge if possible" 1>&2
        echo "  [R]evert    Revert to base version (${labelOlder})" 1>&2
        echo "  [S]ave      Same as 'I' but writes out rold, rnew, and rmine files to deal with later" 1>&2
        echo "  [diff]      Type 'diff' to diff versions $labelMine and $labelTheirs before making a descision" 1>&2
        echo "  [diff3]     Type 'diff3' to diff all three versions before making a descision" 1>&2
        echo "" 1>&2
        ;;

        *   ) 
        echo "'${answer}' is not an option, try again." 1>&2
        ;;
    esac
}

if [ -z $2 ]
then
    echo ERROR: This script expects to be called by subversion
    exit 1
fi

if [ $2 = "-m" ]
then
    #Setup vars
    labelMine=${4}
    labelOlder=${6}
    labelTheirs=${8}
    mine=${9}
    older=${10}
    theirs=${11}
    output=${9}.svnDiff3TempOutput
    baseFileName=`echo $mine | sed -e "s/.tmp$//"`

    #Prompt user for direction
    while [ 1 ]
    do
        echo "" 1>&2
        echo "${baseFileName} requires merging." 1>&2 
        echo "" 1>&2
        echo "What would you like to do?" 1>&2
        echo "[M]erge [A]ccept [I]gnore [R]evert [D]efault [H]elp" 1>&2 
        promptUser
    done
else
    L="-L"          #Argument option for left label
    R="-L"          #Argument option for right label
    label1=$3       #Left label
    label2=$5       #Right label
    file1=$6        #Left file
    file2=$7        #Right file

    $DIFF $file1 $file2 $L "$label1" $L "$label2" &
    #wait for the command to finish
    wait
fi
exit 0