[RFC PATCH 3/3] fixup! editor: allow for saving/restoring terminal state

["Carlo Marcelo Arenas Belón" <carenas@gmail.com>]

Use DEFAULT_EDITOR instead of another hardcoding of "vi".

Do a minor refactoring to avoid having to call isatty(2) twice,
and while at it, a related reformatting that avoids an overlong
line.

Only check if we should enable saving/restoring the terminal if
the session is interactive.

Add documentation for the configuration variable.

Signed-off-by: Carlo Marcelo Arenas Belón <carenas@gmail.com>
---
All of the commit message is meant to be thrown away once/if
this is squashed into the previous commit.

Signed-off-by could be transformed into a Helped-by if anything
could be of use here otherwise.

 Documentation/config.txt        |  2 ++
 Documentation/config/editor.txt |  8 ++++++++
 editor.c                        | 10 ++++++----
 3 files changed, 16 insertions(+), 4 deletions(-)
 create mode 100644 Documentation/config/editor.txt

diff --git a/Documentation/config.txt b/Documentation/config.txt
index 1167e88e34..342f3cc183 100644
--- a/Documentation/config.txt
+++ b/Documentation/config.txt
@@ -361,6 +361,8 @@ include::config/diff.txt[]
 
 include::config/difftool.txt[]
 
+include::config/editor.txt[]
+
 include::config/extensions.txt[]
 
 include::config/fastimport.txt[]
diff --git a/Documentation/config/editor.txt b/Documentation/config/editor.txt
new file mode 100644
index 0000000000..b65c2810fa
--- /dev/null
+++ b/Documentation/config/editor.txt
@@ -0,0 +1,8 @@
+editor.stty::
+	A boolean variable that tells git to save and restore its
+	terminal settings when the editor is invoked, to avoid
+	being affected by garbled input/output, if it misbehaves.
++
+It defaults to 'true' if your editor is "vi" (which is
+also the default if there is no `core.editor`), or to
+'false' otherwise.
diff --git a/editor.c b/editor.c
index 70d3f80966..12180039d2 100644
--- a/editor.c
+++ b/editor.c
@@ -50,7 +50,7 @@ const char *git_sequence_editor(void)
 
 static int prepare_term(const char *editor)
 {
-	int need_saverestore = !strcmp(editor, "vi");
+	int need_saverestore = !strcmp(editor, DEFAULT_EDITOR);
 
 	git_config_get_bool("editor.stty", &need_saverestore);
 	if (need_saverestore)
@@ -68,8 +68,10 @@ static int launch_specified_editor(const char *editor, const char *path,
 		struct strbuf realpath = STRBUF_INIT;
 		const char *args[] = { editor, NULL, NULL };
 		struct child_process p = CHILD_PROCESS_INIT;
-		int ret, sig, need_restore = 0;
-		int print_waiting_for_editor = advice_enabled(ADVICE_WAITING_FOR_EDITOR) && isatty(2);
+		int ret, sig, need_restore;
+		int is_interactive = isatty(2);
+		int print_waiting_for_editor = advice_enabled(ADVICE_WAITING_FOR_EDITOR) &&
+						is_interactive;
 
 		if (print_waiting_for_editor) {
 			/*
@@ -94,7 +96,7 @@ static int launch_specified_editor(const char *editor, const char *path,
 		p.env = env;
 		p.use_shell = 1;
 		p.trace2_child_class = "editor";
-		need_restore = prepare_term(editor);
+		need_restore = is_interactive ? prepare_term(editor) : 0;
 		if (start_command(&p) < 0) {
 			if (need_restore)
 				restore_term();
-- 
2.34.1.460.g364565cfab