git-mergetool: Make default smarter by considering user's desktop environment and editor

Make git-mergetool prefer meld under GNOME, and kdiff3 under KDE. When considering emerge and vimdiff, check $VISUAL and $EDITOR to see which the user might prefer.

---

Arguably, kdiff3 should now move down next to meld, below the other non-graphical tools, so that if the user doesn't run KDE or GNOME they get a non-KDE, non-GNOME tool. This patch doesn't do that, though.

 git-mergetool.sh |   14 +++++++++++++-
 1 files changed, 13 insertions(+), 1 deletions(-)

index bb21b03..2053d43 100755
@@ -304,7 +304,13 @@ if test -z "$merge_tool"; then
 fi
 
 if test -z "$merge_tool" ; then
-    if type kdiff3 >/dev/null 2>&1 && test -n "$DISPLAY"; then
+    # Try tools that match the user's desktop environment
+    if test x"$KDE_FULL_SESSION" = x"true" && type kdiff3 >/dev/null 2>&1 && test -n "$DISPLAY"; then
+        merge_tool="kdiff3";
+    elif test x"$GNOME_DESKTOP_SESSION_ID" != x"" && type meld >/dev/null 2>&1 && test -n "$DISPLAY"; then
+        merge_tool=meld
+    # Try any graphical tool
+    elif type kdiff3 >/dev/null 2>&1 && test -n "$DISPLAY"; then
 	merge_tool="kdiff3";
     elif type tkdiff >/dev/null 2>&1 && test -n "$DISPLAY"; then
 	merge_tool=tkdiff

@@ -312,6 +318,12 @@ if test -z "$merge_tool" ; then
 	merge_tool=xxdiff
     elif type meld >/dev/null 2>&1 && test -n "$DISPLAY"; then
 	merge_tool=meld
+    # Try tools specific to the user's editor
+    elif echo "${VISUAL:-$EDITOR}" | grep '^emacs' > /dev/null 2>&1 && type emacs >/dev/null 2>&1; then
+	merge_tool=emerge
+    elif echo "${VISUAL:-$EDITOR}" | grep '^vim' > /dev/null 2>&1 && type vimdiff >/dev/null 2>&1; then
+	merge_tool=vimdiff
+    # Try other tools
     elif type opendiff >/dev/null 2>&1; then
 	merge_tool=opendiff
     elif type emacs >/dev/null 2>&1; then

1.5.2.1

The basic idea is sound. However...

(1) I wonder if we can get rid of the horribly long if .. elif

     chain by using shell function and then iterate a list of them;

(2) echo "${VISUAL-$EDITOR}" | grep '^emacs'???

Some people may have explicit path (/home/me/bin/emacs), and/or runs a variant of emacs called 'xemacs'. Same for vim.

Something like...

        test_xstuff () {
                test -n "$DISPLAY" && type "$1" >/dev/null 2>&1
        test_kdiff3 () {
                test_xstuff kdiff3
        }
        test_tkdiff () {
                test_xstuff tkdiff
        }
        test_estuff() {
                type "$1" >/dev/null 2>&1 &&
                case "${VISUAL-$EDITOR}" in *"$1"*) : ;; *) false ;; esac
        }
        test_emerge () {
                test_estuff emacs
        }
        test_vimdiff () {
                test_estuff vim
        }

        choose_merge_tool () {
                for t in "$@"
                do
                        if test_$t
                        then
                                echo "$t"
                                break
                        fi
                done
        }

        if test -z "$merge_tool"
        then
                merge_tool_candidates='kdiff3 tkdiff xxdiff meld opendiff ...'
                if test -n "$GNOME_DESCTOP_SESSION_ID"
                then
                        merge_tool_candidates="meld $merge_tool_candidates"
                elif test -n "$KDE_FULL_SESSION"
                then
                        merge_tool_candidates="kdiff3 $merge_tool_candidates"
                elif
                        ...
                fi
                merge_tool=$(choose_merge_tool $merge_tool_candidates)
        fi

Actually, a lot of people run as editor a program called "emacsclient" or "gnuclient": this one connects to an existing Emacs session and passes its arguments to it. And of course, this is what git-mergetool should then also do.

David Kastrup

I do that too, but that is covered by the prefix rule Josh has, so it is Ok.

Another note: in my usual Emacs session, EDITOR is set to /usr/local/emacs-22/bin/emacsclient
which would not be covered... So that should probably be

useemacs=0
for i in ${VISUAL-$EDITOR}
do

        case "`basename $i`" in [xX][eE]macs*|[eE]macs*|gnuclient*)
             useemacs=1
        esac
        break

done

This should work even when we are talking about something like EDITOR="C:\My Programs\XEmacs\gnuclient.exe" -n "C:\My Programs\XEmacs\XEmacs"

And it does not require starting grep for something which the shell can perfectly well handle on its own. Yes, it does need basename. I don't see a good way to avoid that.

David Kastrup

This is what I've been experimenting in my tree; what do people think?

if test -z "$merge_tool" ; then
if test -n "$DISPLAY"; then
merge_tool_candidates="kdiff3 tkdiff xxdiff meld gvimdiff" if test "$GNOME_DESKTOP_SESSION_ID"x != ""x; then
merge_tool_candidates="meld $merge_tool_candidates"
fi
if test "$KDE_FULL_SESSION"x = "true"x; then
merge_tool_candidates="kdiff3 $merge_tool_candidates"
fi
fi
if echo "${VISUAL:-$EDITOR}" | grep 'emacs' > /dev/null 2>&1; then
merge_tool_candidates="$merge_tool_candidates emerge"
fi
if echo "${VISUAL:-$EDITOR}" | grep 'vim' > /dev/null 2>&1; then
merge_tool_candidates="$merge_tool_candidates vimdiff"
fi
merge_tool_candidates="$merge_tool_candidates opendiff emerge vimdiff" echo "merge tool candidates: $merge_tool_candidates"
for i in $merge_tool_candidates; do
if test $i = emerge ; then
cmd=emacs
else
cmd=$i
fi
if type $cmd > /dev/null 2>&1; then
echo merge_tool chosen is $i
merge_tool=$i
break
fi
done
fi

- Ted