Merge branch 'zk/difftool-counts'

Show the total number of paths and the number of paths shown so far
when "git difftool" prompts to launch an external diff tool, which
would give users some sense of progress.

* zk/difftool-counts:
  diff.c: fix some recent whitespace style violations
  difftool: display the number of files in the diff queue in the prompt

5 files changed, 43 insertions, 4 deletions

diff --git a/Documentation/git.txt b/Documentation/git.txt
index cc0e5e2bfe..aec372646f 100644
--- a/Documentation/git.txt
+++ b/Documentation/git.txt
@@ -807,6 +807,15 @@ temporary file --- it is removed when 'GIT_EXTERNAL_DIFF' exits.
 +
 For a path that is unmerged, 'GIT_EXTERNAL_DIFF' is called with 1
 parameter, <path>.
++
+For each path 'GIT_EXTERNAL_DIFF' is called, two environment variables,
+'GIT_DIFF_PATH_COUNTER' and 'GIT_DIFF_PATH_TOTAL' are set.
+
+'GIT_DIFF_PATH_COUNTER'::
+	A 1-based counter incremented by one for every path.
+
+'GIT_DIFF_PATH_TOTAL'::
+	The total number of paths.
 
 other
 ~~~~~
diff --git a/diff.c b/diff.c
index b79432b1ec..f99bc83b73 100644
--- a/diff.c
+++ b/diff.c
@@ -2899,11 +2899,16 @@ static void run_external_diff(const char *pgm,
 			      struct diff_filespec *one,
 			      struct diff_filespec *two,
 			      const char *xfrm_msg,
-			      int complete_rewrite)
+			      int complete_rewrite,
+			      struct diff_options *o)
 {
 	const char *spawn_arg[10];
 	int retval;
 	const char **arg = &spawn_arg[0];
+	struct diff_queue_struct *q = &diff_queued_diff;
+	const char *env[3] = { NULL };
+	char env_counter[50];
+	char env_total[50];
 
 	if (one && two) {
 		struct diff_tempfile *temp_one, *temp_two;
@@ -2928,7 +2933,14 @@ static void run_external_diff(const char *pgm,
 	}
 	*arg = NULL;
 	fflush(NULL);
-	retval = run_command_v_opt(spawn_arg, RUN_USING_SHELL);
+
+	env[0] = env_counter;
+	snprintf(env_counter, sizeof(env_counter), "GIT_DIFF_PATH_COUNTER=%d",
+		 ++o->diff_path_counter);
+	env[1] = env_total;
+	snprintf(env_total, sizeof(env_total), "GIT_DIFF_PATH_TOTAL=%d", q->nr);
+
+	retval = run_command_v_opt_cd_env(spawn_arg, RUN_USING_SHELL, NULL, env);
 	remove_tempfile();
 	if (retval) {
 		fprintf(stderr, "external diff died, stopping at %s.\n", name);
@@ -3042,7 +3054,7 @@ static void run_diff_cmd(const char *pgm,
 
 	if (pgm) {
 		run_external_diff(pgm, name, other, one, two, xfrm_msg,
-				  complete_rewrite);
+				  complete_rewrite, o);
 		return;
 	}
 	if (one && two)
@@ -3317,6 +3329,8 @@ void diff_setup_done(struct diff_options *options)
 		options->output_format = DIFF_FORMAT_NO_OUTPUT;
 		DIFF_OPT_SET(options, EXIT_WITH_STATUS);
 	}
+
+	options->diff_path_counter = 0;
 }
 
 static int opt_arg(const char *arg, int arg_short, const char *arg_long, int *val)
diff --git a/diff.h b/diff.h
index 1c05b3a6be..760388fa17 100644
--- a/diff.h
+++ b/diff.h
@@ -164,6 +164,8 @@ struct diff_options {
 	diff_prefix_fn_t output_prefix;
 	int output_prefix_length;
 	void *output_prefix_data;
+
+	int diff_path_counter;
 };
 
 enum color_diff {
diff --git a/git-difftool--helper.sh b/git-difftool--helper.sh
index b00ed95dba..7ef36b9482 100755
--- a/git-difftool--helper.sh
+++ b/git-difftool--helper.sh
@@ -40,7 +40,8 @@ launch_merge_tool () {
 	# the user with the real $MERGED name before launching $merge_tool.
 	if should_prompt
 	then
-		printf "\nViewing: '%s'\n" "$MERGED"
+		printf "\nViewing (%s/%s): '%s'\n" "$GIT_DIFF_PATH_COUNTER" \
+			"$GIT_DIFF_PATH_TOTAL" "$MERGED"
 		if use_ext_cmd
 		then
 			printf "Launch '%s' [Y/n]: " \
diff --git a/t/t4020-diff-external.sh b/t/t4020-diff-external.sh
index 8a309795c9..bcae35ac1c 100755
--- a/t/t4020-diff-external.sh
+++ b/t/t4020-diff-external.sh
@@ -193,6 +193,19 @@ test_expect_success 'GIT_EXTERNAL_DIFF with more than one changed files' '
 	GIT_EXTERNAL_DIFF=echo git diff
 '
 
+test_expect_success 'GIT_EXTERNAL_DIFF path counter/total' '
+	write_script external-diff.sh <<-\EOF &&
+	echo $GIT_DIFF_PATH_COUNTER of $GIT_DIFF_PATH_TOTAL >>counter.txt
+	EOF
+	>counter.txt &&
+	cat >expect <<-\EOF &&
+	1 of 2
+	2 of 2
+	EOF
+	GIT_EXTERNAL_DIFF=./external-diff.sh git diff &&
+	test_cmp expect counter.txt
+'
+
 test_expect_success 'GIT_EXTERNAL_DIFF generates pretty paths' '
 	touch file.ext &&
 	git add file.ext &&