#!/bin/sh

# Script to get stable diff output on any platform.

#

# Output of this script is almost equivalent to GNU diff with "-Nru".

#

# Use this script as "hg pdiff" via extdiff extension with preparation

# below in test scripts:

#

#   $ cat >> $HGRCPATH <<EOF

#   > [extdiff]

#   > pdiff = sh "$RUNTESTDIR/pdiff"

#   > EOF

filediff(){

    # USAGE: filediff file1 file2 [header]

    # compare with /dev/null if file doesn't exist (as "-N" option)

    file1="$1"

    if test ! -f "$file1"; then

        file1=/dev/null

    fi

    file2="$2"

    if test ! -f "$file2"; then

        file2=/dev/null

    fi

    if cmp -s "$file1" "$file2" 2> /dev/null; then

        # Return immediately, because comparison isn't needed. This

        # also avoids redundant message of diff like "No differences

        # encountered" (on Solaris)

        return

    fi

    if test -n "$3"; then

        # show header only in recursive case

        echo "$3"

    fi

    # replace "/dev/null" by corresponded filename (as "-N" option)

    diff -u "$file1" "$file2" |

    sed "s@^--- /dev/null\(.*\)\$@--- $1\1@" |

    sed "s@^\+\+\+ /dev/null\(.*\)\$@+++ $2\1@"

    # in this case, files differ from each other

    return 1

}

if test -d "$1" -o -d "$2"; then

    # ensure comparison in dictionary order

    (

    if test -d "$1"; then (cd "$1" && find . -type f); fi

    if test -d "$2"; then (cd "$2" && find . -type f); fi

    ) |

    sed 's@^\./@@g' | sort | uniq |

    while read file; do

        filediff "$1/$file" "$2/$file" "diff -Nru $1/$file $2/$file"

    done

    # TODO: there is no portable way for current while-read based

    # implementation to return 1 at detecting changes.

    #

    # On bash and dash, assignment to variable inside while-block

    # doesn't affect outside, because inside while-block is executed

    # in sub-shell. BTW, it affects outside while-block on ksh (as sh

    # on Solaris).

else

    filediff "$1" "$2"

fi