hgmerge: fix diff+patch detection; cleanups

Details:
  - actually show help message when no tools are found
  - whitespace cleanup (stupid emacs)
  - quote more variables
  - simplify merge/diff3 error handling

hgmerge

@@ -1,167 +1,168 b''
 #!/bin/sh
 #
 # hgmerge - default merge helper for Mercurial
 #
 # This tries to find a way to do three-way merge on the current system.
 # The result ought to end up in $1.
 
 set -e # bail out quickly on failure
 
 LOCAL="$1"
 BASE="$2"
 OTHER="$3"
 
 if [ -z "$EDITOR" ]; then
     EDITOR="vi"
 fi
 
 # find decent versions of our utilities, insisting on the GNU versions where we
 # need to
-MERGE=merge
-DIFF3=gdiff3
-DIFF=gdiff
-PATCH=gpatch
+MERGE="merge"
+DIFF3="gdiff3"
+DIFF="gdiff"
+PATCH="gpatch"
 
-type $MERGE >/dev/null 2>&1 || MERGE=
-type $DIFF3 >/dev/null 2>&1 || DIFF3=diff3
-type $DIFF  >/dev/null 2>&1 || DIFF=diff
-type $PATCH >/dev/null 2>&1 || PATCH=patch
+type "$MERGE" >/dev/null 2>&1 || MERGE=
+type "$DIFF3" >/dev/null 2>&1 || DIFF3="diff3"
 $DIFF3 --version >/dev/null 2>&1 || DIFF3=
+type "$DIFF"  >/dev/null 2>&1 || DIFF="diff"
+type "$DIFF"  >/dev/null 2>&1 || DIFF=
+type "$PATCH" >/dev/null 2>&1 || PATCH="patch"
+type "$PATCH" >/dev/null 2>&1 || PATCH=
 
 # find optional visual utilities
-FILEMERGE='/Developer/Applications/Utilities/FileMerge.app/Contents/MacOS/FileMerge'
-KDIFF3=kdiff3
-TKDIFF=tkdiff
+FILEMERGE="/Developer/Applications/Utilities/FileMerge.app/Contents/MacOS/FileMerge"
+KDIFF3="kdiff3"
+TKDIFF="tkdiff"
 
-type $FILEMERGE >/dev/null 2>&1 || FILEMERGE=
-type $KDIFF3    >/dev/null 2>&1 || KDIFF3=
-type $TKDIFF    >/dev/null 2>&1 || TKDIFF=
+type "$FILEMERGE" >/dev/null 2>&1 || FILEMERGE=
+type "$KDIFF3"    >/dev/null 2>&1 || KDIFF3=
+type "$TKDIFF"    >/dev/null 2>&1 || TKDIFF=
 
 # random part of names
-RAND="$RANDOM.$RANDOM.$RANDOM.$$"
+RAND="$RANDOM$RANDOM"
 
 # temporary directory for diff+patch merge
-HGTMP="${TMPDIR-/tmp}/hgmerge.$RAND"
+HGTMP="${TMPDIR-'/tmp'}/hgmerge.$RAND"
 
 # backup file
 BACKUP="$LOCAL.orig.$RAND"
 
 # file used to test for file change
 CHGTEST="$LOCAL.chg.$RAND"
 
 # put all your required cleanup here
 cleanup() {
     rm -f "$BACKUP" "$CHGTEST"
     rm -rf "$HGTMP"
 }
 
 # functions concerning program exit
 success() {
     cleanup
     exit 0
 }
 
 failure() {
     echo "merge failed" 1>&2
     mv "$BACKUP" "$LOCAL"
     cleanup
     exit 1
 }
 
 # Clean up when interrupted
 trap "failure" 1 2 3 6 15 # HUP INT QUIT ABRT TERM
 
 # Back up our file (and try hard to keep the mtime unchanged)
 mv "$LOCAL" "$BACKUP"
 cp "$BACKUP" "$LOCAL"
 
 # Attempt to do a non-interactive merge
+if [ -n "$MERGE" -o -n "$DIFF3" ]; then
 if [ -n "$MERGE" ]; then
     $MERGE "$LOCAL" "$BASE" "$OTHER" 2> /dev/null && success
-    cp "$BACKUP" "$LOCAL"
 elif [ -n "$DIFF3" ]; then
-    echo $DIFF3 -m "$BACKUP" "$BASE" "$OTHER"
     $DIFF3 -m "$BACKUP" "$BASE" "$OTHER" > "$LOCAL" && success
-    if [ $? -eq 2 ]; then
-        echo "$DIFF3 failed! Exiting." 1>&2
-        cp "$BACKUP" "$LOCAL"
+    fi
+    if [ $? -gt 1 ]; then
+        echo "automatic merge failed! Exiting." 1>&2
         failure
     fi
+fi
     cp "$BACKUP" "$LOCAL"
-fi
 
 # on MacOS X try FileMerge.app, shipped with Apple's developer tools
 if [ -n "$FILEMERGE" ]; then
     cp "$BACKUP" "$LOCAL"
     cp "$BACKUP" "$CHGTEST"
     # filemerge prefers the right by default
     $FILEMERGE -left "$OTHER" -right "$LOCAL" -ancestor "$BASE" -merge "$LOCAL"
     [ $? -ne 0 ] && echo "FileMerge failed to launch" && failure
     if test "$LOCAL" -nt "$CHGTEST"
     then
         success
     else
         echo "$LOCAL seems unchanged. Was the merge successful?"
         select answer in yes no
         do
             test "$answer" == "yes" && success || failure
         done
     fi
     failure
 fi
 
 if [ -n "$DISPLAY" ]; then
     # try using kdiff3, which is fairly nice
     if [ -n "$KDIFF3" ]; then
 	$KDIFF3 --auto "$BASE" "$LOCAL" "$OTHER" -o "$LOCAL" || failure
 	success
     fi
 
     # try using tkdiff, which is a bit less sophisticated
     if [ -n "$TKDIFF" ]; then
 	$TKDIFF "$LOCAL" "$OTHER" -a "$BASE" -o "$LOCAL" || failure
 	success
     fi
 fi
 
 # Attempt to do a merge with $EDITOR
 if [ -n "$MERGE" ]; then
     echo "conflicts detected in $LOCAL"
     $MERGE "$LOCAL" "$BASE" "$OTHER" 2>/dev/null || $EDITOR "$LOCAL"
     success
 fi
 
 if [ -n "$DIFF3" ]; then
     echo "conflicts detected in $LOCAL"
     $DIFF3 -m "$BACKUP" "$BASE" "$OTHER" > "$LOCAL" || {
         case $? in
             1)
                 $EDITOR "$LOCAL" ;;
             2)  echo "$DIFF3 failed! Exiting." 1>&2
                 cp "$BACKUP" "$LOCAL"
                 failure ;;
         esac
         success
     }
 fi
 
 # attempt to manually merge with diff and patch
 if [ -n "$DIFF" -a -n "$PATCH" ]; then
 
     (umask 077 && mkdir "$HGTMP") || {
 	echo "Could not create temporary directory $HGTMP" 1>&2
 	failure
     }
 
     $DIFF -u "$BASE" "$OTHER" > "$HGTMP/diff" || :
     if $PATCH "$LOCAL" < "$HGTMP/diff"; then
 	success
     else
 	# If rejects are empty after using the editor, merge was ok
 	$EDITOR "$LOCAL" "$LOCAL.rej" && test -s "$LOCAL.rej" || success
     fi
     failure
 fi
 
 echo "hgmerge: unable to find merge, tkdiff, kdiff3, or diff+patch!"
 failure