Partially un-revert "editor: save and reset terminal after calling EDITOR"

In e3f7e01 (Revert "editor: save and reset terminal after calling
EDITOR", 2021-11-22), we reverted the commit wholesale where the
terminal state would be saved and restored before/after calling an
editor.

The reverted commit was intended to fix a problem with Windows Terminal
where simply calling `vi` would cause problems afterwards.

To fix the problem addressed by the revert, but _still_ keep the problem
with Windows Terminal fixed, let's revert the revert, with a twist: we
restrict the save/restore _specifically_ to the case where `vi` (or
`vim`) is called, and do not do the same for any other editor.

This should still catch the majority of the cases, and will bridge the
time until the original patch is re-done in a way that addresses all
concerns.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

Author: dscho

editor.c

@@ -3,6 +3,7 @@
 #include "strbuf.h"
 #include "run-command.h"
 #include "sigchain.h"
+#include "compat/terminal.h"
 
 #ifndef DEFAULT_EDITOR
 #define DEFAULT_EDITOR "vi"
@@ -54,6 +55,7 @@ static int launch_specified_editor(const char *editor, const char *path,
 		return error("Terminal is dumb, but EDITOR unset");
 
 	if (strcmp(editor, ":")) {
+		int save_and_restore_term = !strcmp(editor, "vi") || !strcmp(editor, "vim");
 		struct strbuf realpath = STRBUF_INIT;
 		const char *args[] = { editor, NULL, NULL };
 		struct child_process p = CHILD_PROCESS_INIT;
@@ -83,14 +85,20 @@ static int launch_specified_editor(const char *editor, const char *path,
 		p.env = env;
 		p.use_shell = 1;
 		p.trace2_child_class = "editor";
+		if (save_and_restore_term)
+			save_and_restore_term = !save_term(1);
 		if (start_command(&p) < 0) {
+			if (save_and_restore_term)
+				restore_term();
 			strbuf_release(&realpath);
 			return error("unable to start editor '%s'", editor);
 		}
 
 		sigchain_push(SIGINT, SIG_IGN);
 		sigchain_push(SIGQUIT, SIG_IGN);
 		ret = finish_command(&p);
+		if (save_and_restore_term)
+			restore_term();
 		strbuf_release(&realpath);
 		sig = ret - 128;
 		sigchain_pop(SIGINT);