Re: [PATCH v2] launch_editor(): indicate that Git waits for user input

[Eric Sunshine <sunshine@sunshineco.com>]

On Fri, Nov 17, 2017 at 8:51 AM,  <lars.schneider@autodesk.com> wrote:
> 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.
>
> Show a message in the original terminal and get rid of it when the
> editor returns.
>
> Signed-off-by: Junio C Hamano <gitster@pobox.com>
> Signed-off-by: Lars Schneider <larsxschneider@gmail.com>
> ---
> diff --git a/editor.c b/editor.c
> @@ -40,6 +40,32 @@ int launch_editor(const char *path, struct strbuf *buffer, const char *const *en
> +               static const char *close_notice = NULL;
> +
> +               if (isatty(2) && !close_notice) {

If you reverse this condition to say (!close_notice && isatty(2)),
then you save an isatty() invocation each time if close_notice is
already assigned.

However, it's not clear how much benefit you gain from stashing this
away in a static variable. Premature optimization?

> +                       char *term = getenv("TERM");
> +
> +                       if (term && strcmp(term, "dumb"))
> +                               /*
> +                                * go back to the beginning and erase the
> +                                * entire line if the terminal is capable
> +                                * to do so, to avoid wasting the vertical
> +                                * space.
> +                                */
> +                               close_notice = "\r\033[K";
> +                       else
> +                               /* otherwise, complete and waste the line */
> +                               close_notice = "done.\n";
> +               }
> +
> +               if (close_notice) {
> +                       fprintf(
> +                               stderr,
> +                               "Launched your editor ('%s'). Adjust, save, and close the "
> +                               "file to continue. Waiting for your input... ", editor
> +                       );

Here's what this looks like for me:

--- 8< ---
Launched your editor
('/Applications/Emacs.app/Contents/MacOS/bin/emacsclient'). Adjust,
save, and close the file to continue. Waiting for your input...
Waiting for Emacs...
--- 8< ---

Very, very noisy, so much so that it's almost unreadable. There are at
least three reasons for the noise:

* The raw message itself is already overly long. Do we really need to
assume that newcomers are so clueless that they need it spelled out to
such a level of detail? "Launched editor" should be enough for most
people, and one would hope that "Launched editor; waiting for
input..." would be enough for the rest.

* Does not take into consideration that EDITOR might be very long;
perhaps you could just print the basename and strip arguments (i.e.
"/my/long/path/edit -x --foo --zap" becomes "edit"). Or, just omit the
editor altogether.

* emacsclient already prints its own message ("Waiting for Emacs...",
which runs together with Git's message). Perhaps treat emacsclient as
a special case and skip printing this message if emacsclient is in
use: if (strstr(...,"emacsclient"))

And, of course, with a "dumb" terminal, it's even noisier with the
extra "done." at the end:

--- 8< ---
Launched your editor
('/Applications/Emacs.app/Contents/MacOS/bin/emacsclient'). Adjust,
save, and close the file to continue. Waiting for your input...
Waiting for Emacs...
done.
--- 8< ---

As Junio pointed out in [1], emacsclient has already emitted a
newline, so the clear-line sequence is ineffective; likewise, for a
dumb terminal, "done." ends up on its own line. Aside from the noise,
this also suggests making a special case for emacsclient.

And, as Junio pointed out in [2], with a message so long, once it has
wrapped, the clear-line sequence does not work as intended. For those
of us with 80-column terminals, we're left with a bunch of noise on
the screen.

> +                       fflush(stderr);
> +               }
>
>                 p.argv = args;
>                 p.env = env;
> @@ -53,11 +79,14 @@ int launch_editor(const char *path, struct strbuf *buffer, const char *const *en
>                 sig = ret - 128;
>                 sigchain_pop(SIGINT);
>                 sigchain_pop(SIGQUIT);
> +
>                 if (sig == SIGINT || sig == SIGQUIT)
>                         raise(sig);
>                 if (ret)
>                         return error("There was a problem with the editor '%s'.",
>                                         editor);
> +               if (close_notice)
> +                       fputs(close_notice, stderr);

Should printing of close_notice be done before the error()? Otherwise,
you get this:

--- 8< ---
Launched your editor (...) ...There was a problem...
--- 8< ---

>         }

[1]: https://public-inbox.org/git/xmqqr2syvjxb.fsf@gitster.mtv.corp.google.com/
[2]: https://public-inbox.org/git/xmqqy3n4rbnr.fsf@gitster.mtv.corp.google.com/