launch_editor(): indicate that Git waits for user inputls/editor-waiting-message

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 might 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, if the terminal
supports erasing the last line.  Also, make sure that our message is
terminated with a whitespace so that any message the editor may show
upon starting up will be kept separate from our message.

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>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

4 files changed, 30 insertions, 0 deletions

diff --git a/Documentation/config.txt b/Documentation/config.txt
index 9593bfabaa..6ebc50eea8 100644
--- a/Documentation/config.txt
+++ b/Documentation/config.txt
@@ -351,6 +351,9 @@ advice.*::
 	addEmbeddedRepo::
 		Advice on what to do when you've accidentally added one
 		git repo inside of another.
+	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 d81e1cb742..af29d23e43 100644
--- a/advice.c
+++ b/advice.c
@@ -17,6 +17,7 @@ int advice_set_upstream_failure = 1;
 int advice_object_name_warning = 1;
 int advice_rm_hints = 1;
 int advice_add_embedded_repo = 1;
+int advice_waiting_for_editor = 1;
 
 static struct {
 	const char *name;
@@ -38,6 +39,7 @@ static struct {
 	{ "objectnamewarning", &advice_object_name_warning },
 	{ "rmhints", &advice_rm_hints },
 	{ "addembeddedrepo", &advice_add_embedded_repo },
+	{ "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 c84a44531c..f7cbbd342f 100644
--- a/advice.h
+++ b/advice.h
@@ -19,6 +19,7 @@ extern int advice_set_upstream_failure;
 extern int advice_object_name_warning;
 extern int advice_rm_hints;
 extern int advice_add_embedded_repo;
+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..9a9b4e12d1 100644
--- a/editor.c
+++ b/editor.c
@@ -45,6 +45,23 @@ 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);
+
+		if (print_waiting_for_editor) {
+			/*
+			 * A dumb terminal cannot erase the line later on. Add a
+			 * newline to separate the hint from subsequent output.
+			 *
+			 * Make sure that our message is separated with a whitespace
+			 * from further cruft that may be written by the editor.
+			 */
+			const char term = is_terminal_dumb() ? '\n' : ' ';
+
+			fprintf(stderr,
+				_("hint: Waiting for your editor to close the file...%c"),
+				term);
+			fflush(stderr);
+		}
 
 		p.argv = args;
 		p.env = env;
@@ -63,6 +80,13 @@ 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 && !is_terminal_dumb())
+			/*
+			 * Go back to the beginning and erase the entire line to
+			 * avoid wasting the vertical space.
+			 */
+			fputs("\r\033[K", stderr);
 	}
 
 	if (!buffer)