Merge branch 'dl/difftool-mergetool' into pu

Update "git difftool" and "git mergetool" so that the combinations
of {diff,merge}.{tool,guitool} configuration variables serve as
fallback settings of each other in a sensible order.

* dl/difftool-mergetool:
  difftool: fallback on merge.guitool
  difftool: make --gui, --tool and --extcmd mutually exclusive
  mergetool: fallback to tool when guitool unavailable
  mergetool: use get_merge_tool function
  t7610: add mergetool --gui tests
  t7610: unsuppress output

Author: gitster

Documentation/git-difftool.txt

@@ -90,7 +90,9 @@ instead.  `--no-symlinks` is the default on Windows.
 	When 'git-difftool' is invoked with the `-g` or `--gui` option
 	the default diff tool will be read from the configured
 	`diff.guitool` variable instead of `diff.tool`. The `--no-gui`
-	option can be used to override this setting.
+	option can be used to override this setting. If `diff.guitool`
+	is not set, we will fallback in the order of `merge.guitool`,
+	`diff.tool`, `merge.tool` until a tool is found.
 
 --[no-]trust-exit-code::
 	'git-difftool' invokes a diff tool individually on each file.

Documentation/git-mergetool--lib.txt

@@ -28,7 +28,9 @@ to define the operation mode for the functions listed below.
 FUNCTIONS
 ---------
 get_merge_tool::
-	returns a merge tool.
+	returns a merge tool. the return code is 1 if we returned a guessed
+	merge tool, else 0. '$GIT_MERGETOOL_GUI' may be set to 'true' to
+	search for the appropriate guitool.
 
 get_merge_tool_cmd::
 	returns the custom command for a merge tool.

Documentation/git-mergetool.txt

@@ -83,7 +83,9 @@ success of the resolution after the custom tool has exited.
 --gui::
 	When 'git-mergetool' is invoked with the `-g` or `--gui` option
 	the default merge tool will be read from the configured
-	`merge.guitool` variable instead of `merge.tool`.
+	`merge.guitool` variable instead of `merge.tool`. If
+	`merge.guitool` is not set, we will fallback to the tool
+	configured under `merge.tool`.
 
 --no-gui::
 	This overrides a previous `-g` or `--gui` setting and reads the

builtin/difftool.c

@@ -24,7 +24,6 @@
 #include "object-store.h"
 #include "dir.h"
 
-static char *diff_gui_tool;
 static int trust_exit_code;
 
 static const char *const builtin_difftool_usage[] = {
@@ -34,11 +33,6 @@ static const char *const builtin_difftool_usage[] = {
 
 static int difftool_config(const char *var, const char *value, void *cb)
 {
-	if (!strcmp(var, "diff.guitool")) {
-		diff_gui_tool = xstrdup(value);
-		return 0;
-	}
-
 	if (!strcmp(var, "difftool.trustexitcode")) {
 		trust_exit_code = git_config_bool(var, value);
 		return 0;
@@ -736,8 +730,11 @@ int cmd_difftool(int argc, const char **argv, const char *prefix)
 	} else if (dir_diff)
 		die(_("--dir-diff is incompatible with --no-index"));
 
-	if (use_gui_tool && diff_gui_tool && *diff_gui_tool)
-		setenv("GIT_DIFF_TOOL", diff_gui_tool, 1);
+	if (use_gui_tool + !!difftool_cmd + !!extcmd > 1)
+		die(_("--gui, --tool and --extcmd are mutually exclusive"));
+
+	if (use_gui_tool)
+		setenv("GIT_MERGETOOL_GUI", "true", 1);
 	else if (difftool_cmd) {
 		if (*difftool_cmd)
 			setenv("GIT_DIFF_TOOL", difftool_cmd, 1);

git-difftool--helper.sh

@@ -71,7 +71,7 @@ then
 	then
 		merge_tool="$GIT_DIFF_TOOL"
 	else
-		merge_tool="$(get_merge_tool)" || exit
+		merge_tool="$(get_merge_tool)"
 	fi
 fi
 

git-mergetool--lib.sh

@@ -351,20 +351,29 @@ guess_merge_tool () {
 }
 
 get_configured_merge_tool () {
-	# If first argument is true, find the guitool instead
-	if test "$1" = true
+	is_gui="$1"
+	sections="merge"
+	keys="tool"
+
+	if diff_mode
 	then
-		gui_prefix=gui
+		sections="diff $sections"
 	fi
 
-	# Diff mode first tries diff.(gui)tool and falls back to merge.(gui)tool.
-	# Merge mode only checks merge.(gui)tool
-	if diff_mode
+	if "$is_gui" = true
 	then
-		merge_tool=$(git config diff.${gui_prefix}tool || git config merge.${gui_prefix}tool)
-	else
-		merge_tool=$(git config merge.${gui_prefix}tool)
+		keys="guitool $keys"
 	fi
+
+	IFS=' '
+	for key in $keys
+	do
+		for section in $sections
+		do
+			merge_tool=$(git config $section.$key) && break 2
+		done
+	done
+
 	if test -n "$merge_tool" && ! valid_tool "$merge_tool"
 	then
 		echo >&2 "git config option $TOOL_MODE.${gui_prefix}tool set to unknown tool: $merge_tool"
@@ -404,14 +413,17 @@ get_merge_tool_path () {
 }
 
 get_merge_tool () {
+	not_guessed=true
 	# Check if a merge tool has been configured
-	merge_tool=$(get_configured_merge_tool)
+	merge_tool=$(get_configured_merge_tool $GIT_MERGETOOL_GUI)
 	# Try to guess an appropriate merge tool if no tool has been set.
 	if test -z "$merge_tool"
 	then
 		merge_tool=$(guess_merge_tool) || exit
+		not_guessed=false
 	fi
 	echo "$merge_tool"
+	test "$not_guessed" = true
 }
 
 mergetool_find_win32_cmd () {

git-mergetool.sh

@@ -389,7 +389,7 @@ print_noop_and_exit () {
 
 main () {
 	prompt=$(git config --bool mergetool.prompt)
-	gui_tool=false
+	GIT_MERGETOOL_GUI=false
 	guessed_merge_tool=false
 	orderfile=
 
@@ -416,10 +416,10 @@ main () {
 			esac
 			;;
 		--no-gui)
-			gui_tool=false
+			GIT_MERGETOOL_GUI=false
 			;;
 		-g|--gui)
-			gui_tool=true
+			GIT_MERGETOOL_GUI=true
 			;;
 		-y|--no-prompt)
 			prompt=false
@@ -449,12 +449,8 @@ main () {
 
 	if test -z "$merge_tool"
 	then
-		# Check if a merge tool has been configured
-		merge_tool=$(get_configured_merge_tool $gui_tool)
-		# Try to guess an appropriate merge tool if no tool has been set.
-		if test -z "$merge_tool"
+		if ! merge_tool=$(get_merge_tool)
 		then
-			merge_tool=$(guess_merge_tool) || exit
 			guessed_merge_tool=true
 		fi
 	fi