hgeditor

convert: fix convert dropping p2 contents during filemap merge

When converting a merge commit using a filemap convert (i.e. when moving
contents from the root of the repo into subdir1/), convert would silently drop
the entire contents of the target repo's p2. This was because when it built the
target commit, it did so by taking the target p1 and adding only the files that
changed in the source repo's merge commit.

This breaks in the case where the target repo has files that are unrelated to
the source repo (like in the case where you use convert to import a repo as a
subdirectory of another).

The fix is to use Mercurial's merge logic to detect which files in p2 we should
carry over to the merge. It follows three rules:

1) if the file belongs to the source, don't try to merge it. Rely on the list of
files provided to putcommit to be correct.

2) if the file requires merging or user input (change vs deleted), throw an
exception. We don't have enough info to do this.

3) if p2 has the newest, non-merge-requiring version of the file, take it

I've also added a test to cover this issue.

#!/bin/sh
#
# This is an example of using HGEDITOR to create of diff to review the
# changes while commiting.

# If you want to pass your favourite editor some other parameters
# only for Mercurial, modify this:
case "${EDITOR}" in
    "")
        EDITOR="vi"
        ;;
    emacs)
        EDITOR="$EDITOR -nw"
        ;;
    gvim|vim)
        EDITOR="$EDITOR -f -o"
        ;;
esac


HGTMP=""
cleanup_exit() {
    rm -rf "$HGTMP"
}

# Remove temporary files even if we get interrupted
trap "cleanup_exit" 0 # normal exit
trap "exit 255" HUP INT QUIT ABRT TERM

HGTMP=$(mktemp -d ${TMPDIR-/tmp}/hgeditor.XXXXXX)
[ x$HGTMP != x -a -d $HGTMP ] || {
  echo "Could not create temporary directory! Exiting." 1>&2
  exit 1
}

(
    grep '^HG: changed' "$1" | cut -b 13- | while read changed; do
        "$HG" diff "$changed" >> "$HGTMP/diff"
    done
)

cat "$1" > "$HGTMP/msg"

MD5=$(which md5sum 2>/dev/null) || \
    MD5=$(which md5 2>/dev/null)
[ -x "${MD5}" ] && CHECKSUM=`${MD5} "$HGTMP/msg"`
if [ -s "$HGTMP/diff" ]; then
    $EDITOR "$HGTMP/msg" "$HGTMP/diff" || exit $?
else
    $EDITOR "$HGTMP/msg" || exit $?
fi
[ -x "${MD5}" ] && (echo "$CHECKSUM" | ${MD5} -c >/dev/null 2>&1 && exit 13)

mv "$HGTMP/msg" "$1"

exit $?