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

@@ -17,31 +17,33 b' 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"
@@ -76,19 +78,18 b' 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