[PATCH v4 2/2] launch_editor(): indicate that Git waits for user input

[lars.schneider@autodesk.com]

From: Lars Schneider <larsxschneider@gmail.com>

When a graphical GIT_EDITOR is spawned by a Git command that opens
and waits for user input (e.g. "git rebase -i"), then the editor window
might be obscured by other windows. The user may be left staring at the
original Git terminal window without even realizing that s/he needs to
interact with another window before Git can proceed. To this user Git
appears hanging.

Print a message that Git is waiting for editor input in the original
terminal and get rid of it when the editor returns.

No message is printed in a "dumb" terminal as it would not be possible
to remove the message after the editor returns. This should not be a
problem as this feature is targeted at novice Git users and they are
unlikely to work with a "dumb" terminal.

Power users might not want to see this message or their editor might
already print such a message (e.g. emacsclient). Allow these users to
suppress the message by disabling the "advice.waitingForEditor" config.

The standard advise() function is not used here as it would always add
a newline which would make deleting the message harder.

Helped-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Lars Schneider <larsxschneider@gmail.com>
---
 Documentation/config.txt |  3 +++
 advice.c                 |  2 ++
 advice.h                 |  1 +
 editor.c                 | 15 +++++++++++++++
 4 files changed, 21 insertions(+)

diff --git a/Documentation/config.txt b/Documentation/config.txt
index 671fcbaa0f..de64201e82 100644
--- a/Documentation/config.txt
+++ b/Documentation/config.txt
@@ -354,6 +354,9 @@ advice.*::
 	ignoredHook::
 		Advice shown if an hook is ignored because the hook is not
 		set as executable.
+	waitingForEditor::
+		Print a message to the terminal whenever Git is waiting for
+		editor input from the user.
 --
 
 core.fileMode::
diff --git a/advice.c b/advice.c
index c6169bcb52..406efc183b 100644
--- a/advice.c
+++ b/advice.c
@@ -18,6 +18,7 @@ int advice_object_name_warning = 1;
 int advice_rm_hints = 1;
 int advice_add_embedded_repo = 1;
 int advice_ignored_hook = 1;
+int advice_waiting_for_editor = 1;
 
 static struct {
 	const char *name;
@@ -40,6 +41,7 @@ static struct {
 	{ "rmhints", &advice_rm_hints },
 	{ "addembeddedrepo", &advice_add_embedded_repo },
 	{ "ignoredhook", &advice_ignored_hook },
+	{ "waitingforeditor", &advice_waiting_for_editor },
 
 	/* make this an alias for backward compatibility */
 	{ "pushnonfastforward", &advice_push_update_rejected }
diff --git a/advice.h b/advice.h
index f525d6f89c..70568fa792 100644
--- a/advice.h
+++ b/advice.h
@@ -20,6 +20,7 @@ extern int advice_object_name_warning;
 extern int advice_rm_hints;
 extern int advice_add_embedded_repo;
 extern int advice_ignored_hook;
+extern int advice_waiting_for_editor;
 
 int git_default_advice_config(const char *var, const char *value);
 __attribute__((format (printf, 1, 2)))
diff --git a/editor.c b/editor.c
index c65ea698eb..cdad4f74ec 100644
--- a/editor.c
+++ b/editor.c
@@ -45,6 +45,13 @@ int launch_editor(const char *path, struct strbuf *buffer, const char *const *en
 		const char *args[] = { editor, real_path(path), NULL };
 		struct child_process p = CHILD_PROCESS_INIT;
 		int ret, sig;
+		int print_waiting_for_editor = advice_waiting_for_editor &&
+			isatty(2) && !is_terminal_dumb();
+
+		if (print_waiting_for_editor) {
+			fprintf(stderr, _("hint: Waiting for your editor input..."));
+			fflush(stderr);
+		}
 
 		p.argv = args;
 		p.env = env;
@@ -63,6 +70,14 @@ int launch_editor(const char *path, struct strbuf *buffer, const char *const *en
 		if (ret)
 			return error("There was a problem with the editor '%s'.",
 					editor);
+
+		if (print_waiting_for_editor)
+			/*
+			 * go back to the beginning and erase the
+			 * entire line to avoid wasting the vertical
+			 * space.
+			 */
+			fputs("\r\033[K", stderr);
 	}
 
 	if (!buffer)
-- 
2.15.0