mergetool: honor mergetool.$tool.trustExitCode for built-in tools

Built-in merge tools contain a hard-coded assumption about
whether or not a tool's exit code can be trusted to determine
the success or failure of a merge.  Tools whose exit codes are
not trusted contain calls to check_unchanged() in their
merge_cmd() functions.

A problem with this is that the trustExitCode configuration is
not honored for built-in tools.

Teach built-in tools to honor the trustExitCode configuration.
Extend run_merge_cmd() so that it is responsible for calling
check_unchanged() when a tool's exit code cannot be trusted.
Remove check_unchanged() calls from scriptlets since they are no
longer responsible for calling it.

When no configuration is present, exit_code_trustable() is
checked to see whether the exit code should be trusted.
The default implementation returns false.

Tools whose exit codes can be trusted override
exit_code_trustable() to true.

Reported-by: Dun Peal <dunpealer@gmail.com>
Signed-off-by: David Aguilar <davvid@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

19 files changed, 26 insertions, 27 deletions

diff --git a/mergetools/araxis b/mergetools/araxis
index 64f97c5e97..e2407b65b7 100644
--- a/mergetools/araxis
+++ b/mergetools/araxis
@@ -3,7 +3,6 @@ diff_cmd () {
 }
 
 merge_cmd () {
-	touch "$BACKUP"
 	if $base_present
 	then
 		"$merge_tool_path" -wait -merge -3 -a1 \
@@ -12,7 +11,6 @@ merge_cmd () {
 		"$merge_tool_path" -wait -2 \
 			"$LOCAL" "$REMOTE" "$MERGED" >/dev/null 2>&1
 	fi
-	check_unchanged
 }
 
 translate_merge_tool_path() {
diff --git a/mergetools/bc b/mergetools/bc
index b6319d206e..3a69e60faa 100644
--- a/mergetools/bc
+++ b/mergetools/bc
@@ -3,7 +3,6 @@ diff_cmd () {
 }
 
 merge_cmd () {
-	touch "$BACKUP"
 	if $base_present
 	then
 		"$merge_tool_path" "$LOCAL" "$REMOTE" "$BASE" \
@@ -12,7 +11,6 @@ merge_cmd () {
 		"$merge_tool_path" "$LOCAL" "$REMOTE" \
 			-mergeoutput="$MERGED"
 	fi
-	check_unchanged
 }
 
 translate_merge_tool_path() {
diff --git a/mergetools/codecompare b/mergetools/codecompare
index 3f0486bc80..9f60e8da65 100644
--- a/mergetools/codecompare
+++ b/mergetools/codecompare
@@ -3,7 +3,6 @@ diff_cmd () {
 }
 
 merge_cmd () {
-	touch "$BACKUP"
 	if $base_present
 	then
 		"$merge_tool_path" -MF="$LOCAL" -TF="$REMOTE" -BF="$BASE" \
@@ -12,7 +11,6 @@ merge_cmd () {
 		"$merge_tool_path" -MF="$LOCAL" -TF="$REMOTE" \
 			-RF="$MERGED"
 	fi
-	check_unchanged
 }
 
 translate_merge_tool_path() {
diff --git a/mergetools/deltawalker b/mergetools/deltawalker
index b3c71b6236..ee6f374bce 100644
--- a/mergetools/deltawalker
+++ b/mergetools/deltawalker
@@ -16,6 +16,10 @@ merge_cmd () {
 	fi >/dev/null 2>&1
 }
 
-translate_merge_tool_path() {
+translate_merge_tool_path () {
 	echo DeltaWalker
 }
+
+exit_code_trustable () {
+	true
+}
diff --git a/mergetools/diffmerge b/mergetools/diffmerge
index f138cb4e73..9b6355b98a 100644
--- a/mergetools/diffmerge
+++ b/mergetools/diffmerge
@@ -12,3 +12,7 @@ merge_cmd () {
 			--result="$MERGED" "$LOCAL" "$REMOTE"
 	fi
 }
+
+exit_code_trustable () {
+	true
+}
diff --git a/mergetools/diffuse b/mergetools/diffuse
index 02e0843f47..5a3ae8b569 100644
--- a/mergetools/diffuse
+++ b/mergetools/diffuse
@@ -3,7 +3,6 @@ diff_cmd () {
 }
 
 merge_cmd () {
-	touch "$BACKUP"
 	if $base_present
 	then
 		"$merge_tool_path" \
@@ -13,5 +12,4 @@ merge_cmd () {
 		"$merge_tool_path" \
 			"$LOCAL" "$MERGED" "$REMOTE" | cat
 	fi
-	check_unchanged
 }
diff --git a/mergetools/ecmerge b/mergetools/ecmerge
index 13c2e439de..6c5101c4f7 100644
--- a/mergetools/ecmerge
+++ b/mergetools/ecmerge
@@ -3,7 +3,6 @@ diff_cmd () {
 }
 
 merge_cmd () {
-	touch "$BACKUP"
 	if $base_present
 	then
 		"$merge_tool_path" "$BASE" "$LOCAL" "$REMOTE" \
@@ -12,5 +11,4 @@ merge_cmd () {
 		"$merge_tool_path" "$LOCAL" "$REMOTE" \
 			--default --mode=merge2 --to="$MERGED"
 	fi
-	check_unchanged
 }
diff --git a/mergetools/emerge b/mergetools/emerge
index 7b895fdb1f..d1ce513ff5 100644
--- a/mergetools/emerge
+++ b/mergetools/emerge
@@ -20,3 +20,7 @@ merge_cmd () {
 translate_merge_tool_path() {
 	echo emacs
 }
+
+exit_code_trustable () {
+	true
+}
diff --git a/mergetools/examdiff b/mergetools/examdiff
index 7b524d4088..e72b06fc4d 100644
--- a/mergetools/examdiff
+++ b/mergetools/examdiff
@@ -3,14 +3,12 @@ diff_cmd () {
 }
 
 merge_cmd () {
-	touch "$BACKUP"
 	if $base_present
 	then
 		"$merge_tool_path" -merge "$LOCAL" "$BASE" "$REMOTE" -o:"$MERGED" -nh
 	else
 		"$merge_tool_path" -merge "$LOCAL" "$REMOTE" -o:"$MERGED" -nh
 	fi
-	check_unchanged
 }
 
 translate_merge_tool_path() {
diff --git a/mergetools/kdiff3 b/mergetools/kdiff3
index 793d1293b1..0264ed5b20 100644
--- a/mergetools/kdiff3
+++ b/mergetools/kdiff3
@@ -21,3 +21,7 @@ merge_cmd () {
 		>/dev/null 2>&1
 	fi
 }
+
+exit_code_trustable () {
+	true
+}
diff --git a/mergetools/kompare b/mergetools/kompare
index 433686c12a..e8c0bfa678 100644
--- a/mergetools/kompare
+++ b/mergetools/kompare
@@ -5,3 +5,7 @@ can_merge () {
 diff_cmd () {
 	"$merge_tool_path" "$LOCAL" "$REMOTE"
 }
+
+exit_code_trustable () {
+	true
+}
diff --git a/mergetools/meld b/mergetools/meld
index 83ebdfb4c3..bc178e8882 100644
--- a/mergetools/meld
+++ b/mergetools/meld
@@ -7,7 +7,7 @@ merge_cmd () {
 	then
 		check_meld_for_output_version
 	fi
-	touch "$BACKUP"
+
 	if test "$meld_has_output_option" = true
 	then
 		"$merge_tool_path" --output "$MERGED" \
@@ -15,7 +15,6 @@ merge_cmd () {
 	else
 		"$merge_tool_path" "$LOCAL" "$MERGED" "$REMOTE"
 	fi
-	check_unchanged
 }
 
 # Check whether we should use 'meld --output <file>'
diff --git a/mergetools/opendiff b/mergetools/opendiff
index 0942b2a733..b608dd6de3 100644
--- a/mergetools/opendiff
+++ b/mergetools/opendiff
@@ -3,7 +3,6 @@ diff_cmd () {
 }
 
 merge_cmd () {
-	touch "$BACKUP"
 	if $base_present
 	then
 		"$merge_tool_path" "$LOCAL" "$REMOTE" \
@@ -12,5 +11,4 @@ merge_cmd () {
 		"$merge_tool_path" "$LOCAL" "$REMOTE" \
 			-merge "$MERGED" | cat
 	fi
-	check_unchanged
 }
diff --git a/mergetools/p4merge b/mergetools/p4merge
index 5a608abf9c..7a5b291dd2 100644
--- a/mergetools/p4merge
+++ b/mergetools/p4merge
@@ -20,14 +20,12 @@ diff_cmd () {
 }
 
 merge_cmd () {
-	touch "$BACKUP"
 	if ! $base_present
 	then
 		cp -- "$LOCAL" "$BASE"
 		create_virtual_base "$BASE" "$REMOTE"
 	fi
 	"$merge_tool_path" "$BASE" "$REMOTE" "$LOCAL" "$MERGED"
-	check_unchanged
 }
 
 create_empty_file () {
diff --git a/mergetools/tkdiff b/mergetools/tkdiff
index 618c438e87..eee5cb57e3 100644
--- a/mergetools/tkdiff
+++ b/mergetools/tkdiff
@@ -10,3 +10,7 @@ merge_cmd () {
 		"$merge_tool_path" -o "$MERGED" "$LOCAL" "$REMOTE"
 	fi
 }
+
+exit_code_trustable () {
+	true
+}
diff --git a/mergetools/tortoisemerge b/mergetools/tortoisemerge
index 3b89f1c82d..d7ab666a59 100644
--- a/mergetools/tortoisemerge
+++ b/mergetools/tortoisemerge
@@ -5,7 +5,6 @@ can_diff () {
 merge_cmd () {
 	if $base_present
 	then
-		touch "$BACKUP"
 		basename="$(basename "$merge_tool_path" .exe)"
 		if test "$basename" = "tortoisegitmerge"
 		then
@@ -17,7 +16,6 @@ merge_cmd () {
 				-base:"$BASE" -mine:"$LOCAL" \
 				-theirs:"$REMOTE" -merged:"$MERGED"
 		fi
-		check_unchanged
 	else
 		echo "$merge_tool_path cannot be used without a base" 1>&2
 		return 1
diff --git a/mergetools/vimdiff b/mergetools/vimdiff
index 74ea6d5479..a841ffdb49 100644
--- a/mergetools/vimdiff
+++ b/mergetools/vimdiff
@@ -4,7 +4,6 @@ diff_cmd () {
 }
 
 merge_cmd () {
-	touch "$BACKUP"
 	case "$1" in
 	gvimdiff|vimdiff)
 		if $base_present
@@ -31,7 +30,6 @@ merge_cmd () {
 		fi
 		;;
 	esac
-	check_unchanged
 }
 
 translate_merge_tool_path() {
diff --git a/mergetools/winmerge b/mergetools/winmerge
index f3819d316a..74d03259fd 100644
--- a/mergetools/winmerge
+++ b/mergetools/winmerge
@@ -6,10 +6,8 @@ diff_cmd () {
 merge_cmd () {
 	# mergetool.winmerge.trustExitCode is implicitly false.
 	# touch $BACKUP so that we can check_unchanged.
-	touch "$BACKUP"
 	"$merge_tool_path" -u -e -dl Local -dr Remote \
 		"$LOCAL" "$REMOTE" "$MERGED"
-	check_unchanged
 }
 
 translate_merge_tool_path() {
diff --git a/mergetools/xxdiff b/mergetools/xxdiff
index 05b443394b..e284811ff2 100644
--- a/mergetools/xxdiff
+++ b/mergetools/xxdiff
@@ -6,7 +6,6 @@ diff_cmd () {
 }
 
 merge_cmd () {
-	touch "$BACKUP"
 	if $base_present
 	then
 		"$merge_tool_path" -X --show-merged-pane \
@@ -21,5 +20,4 @@ merge_cmd () {
 			-R 'Accel.SearchForward: "Ctrl-G"' \
 			--merged-file "$MERGED" "$LOCAL" "$REMOTE"
 	fi
-	check_unchanged
 }