[RFC PATCH 2/3] mergetools/kdiff3: allow opting-out of auto-merges

[David Aguilar <davvid@gmail.com>]

By default, "git mergetool" passes the `--auto` flag to `kdiff3` when
merging a file.  The `--auto` flag tells `kdiff3` to skip showing the
GUI and automatically save the merged result when it is able to
trivially resolve a merge.

Some users prefer to eyeball the merged result using mergetool and the
use of `--auto` prevents them from doing so.  Add a configuration
variable to allow opting-out of the auto-merge feature.

Signed-off-by: David Aguilar <davvid@gmail.com>
---
Marked "RFC" because I am kinda against adding more configuration
variables.  Someone ran into this and I did personally find the
behavior a bit surprising.  Alternatively, we *could* change the
default behavior, but I am not convinced that doing so is a good idea
either, hence this patch.  Other then the "kinda against",
it does make the behavior less surprising.

 Documentation/merge-config.txt |  9 +++++++++
 mergetools/kdiff3              | 20 ++++++++++++++++++--
 2 files changed, 27 insertions(+), 2 deletions(-)

diff --git a/Documentation/merge-config.txt b/Documentation/merge-config.txt
index d78d6d8..3bd5f21 100644
--- a/Documentation/merge-config.txt
+++ b/Documentation/merge-config.txt
@@ -59,6 +59,15 @@ merge.tool::
 
 include::mergetools-merge.txt[]
 
+mergetool.kdiff3.manualMerge::
+	Tell Git that not to use `kdiff3`'s auto-merge feature.
+	By default, "git mergetool" passes the `--auto` flag to `kdiff3`
+	when merging a file.  The `--auto` flag tells `kdiff3` to skip
+	showing the GUI and automatically save the merged result when it
+	is able to trivially resolve a merge.  The `--auto` flag will
+	not be used when this variable is set to `true`.  False by
+	default.
+
 merge.verbosity::
 	Controls the amount of output shown by the recursive merge
 	strategy.  Level 0 outputs nothing except a final error
diff --git a/mergetools/kdiff3 b/mergetools/kdiff3
index a30034f..d0acda9 100644
--- a/mergetools/kdiff3
+++ b/mergetools/kdiff3
@@ -1,3 +1,18 @@
+kdiff3_initialized=
+kdiff3_args=--auto
+
+kdiff3_init () {
+	if test -n "$kdiff3_initialized"
+	then
+		return
+	fi
+	if test "$(git config --bool mergetool.kdiff3.manualMerge)" = true
+	then
+		kdiff3_args=
+	fi
+	kdiff3_initialized=true
+}
+
 diff_cmd () {
 	"$merge_tool_path" \
 		--L1 "$MERGED (A)" --L2 "$MERGED (B)" \
@@ -5,16 +20,17 @@ diff_cmd () {
 }
 
 merge_cmd () {
+	kdiff3_init
 	if $base_present
 	then
-		"$merge_tool_path" --auto \
+		"$merge_tool_path" $kdiff3_args \
 			--L1 "$MERGED (Base)" \
 			--L2 "$MERGED (Local)" \
 			--L3 "$MERGED (Remote)" \
 			-o "$MERGED" "$BASE" "$LOCAL" "$REMOTE" \
 		>/dev/null 2>&1
 	else
-		"$merge_tool_path" --auto \
+		"$merge_tool_path" $kdiff3_args \
 			--L1 "$MERGED (Local)" \
 			--L2 "$MERGED (Remote)" \
 			-o "$MERGED" "$LOCAL" "$REMOTE" \
-- 
1.8.3.rc1.38.g0f1704c