Subject: Re: [PATCH] rebase: fix garbled progress display with '-x'

From: SZEDER Gábor <[email-masked]>
Date: Thu, 2 May 2019 01:16:40 +0200

On Tue, Apr 30, 2019 at 06:25:35PM -0400, Johannes Schindelin wrote:
> Hi,
> 
> On Tue, 30 Apr 2019, SZEDER Gábor wrote:
> 
> > When running a command with the 'exec' instruction during an
> > interactive rebase session, or for a range of commits using 'git
> > rebase -x', the output can be a bit garbled when the name of the
> > command is short enough:
> >
> >   $ git rebase -x true HEAD~5
> >   Executing: true
> >   Executing: true
> >   Executing: true
> >   Executing: true
> >   Executing: true)
> >   Successfully rebased and updated refs/heads/master.
> >
> > Note the ')' at the end of the last line.  It gets more garbled as the
> > range of commits increases:
> >
> >   $ git rebase -x true HEAD~50
> >   Executing: true)
> >   [ repeated 3 more times ]
> >   Executing: true0)
> >   [ repeated 44 more times ]
> >   Executing: true00)
> >   Successfully rebased and updated refs/heads/master.
> >
> > Those extra numbers and ')' are remnants of the previously displayed
> > "Rebasing (N/M)" progress lines that are usually completely
> > overwritten by the "Executing: <cmd>" lines, unless 'cmd' is short and
> > the "N/M" part is long.
> >
> > Make sure that the previously displayed "Rebasing (N/M)" line is
> > completely covered up by printing a terminal width worth of space
> > characters.
> >
> > Signed-off-by: SZEDER Gábor <[email-masked]>
> 
> Makes sense.
> 
> > This issue has already been present in the scripted rebase as well.
> >
> > As far as I could tell, if any other rebase instruction prints a
> > message, then that tends to be so long (including abbreviated commit
> > OIDs and whatnot) that they practically always overwrite that
> > "Rebasing (N/M)" progress line (well, except, perhaps, when rebasing
> > billions of commits at a time?).
> >
> >  sequencer.c | 6 ++++++
> >  1 file changed, 6 insertions(+)
> >
> > diff --git a/sequencer.c b/sequencer.c
> > index 546f281898..c2e4baa90e 100644
> > --- a/sequencer.c
> > +++ b/sequencer.c
> > @@ -3631,6 +3631,12 @@ static int pick_commits(struct repository *r,
> >  			int saved = *end_of_arg;
> >  			struct stat st;
> >
> > +			if (!opts->verbose)
> > +				/*
> > +				 * Fully cover the previous "Rebasing (n/m)"
> > +				 * progress line.
> > +				 */
> > +				fprintf(stderr, "%*s\r", term_columns(), "");
> 
> IIRC there are terminals (`cmd.exe`?) that would advance to the next row
> automatically when printing the exact number of columns in a row. So this
> would not work.

Hrm, I though about using 'term_columns()-1', or moving the '\r' from
the format string to the string to be printed, but in the end didn't
do either, because it seemed to work well as it is in the two
terminals that I tried (on Linux).

> But isn't there an ANSI sequence that we can use?
> 
> *clicketyclick*
> 
> Yes: https://github.com/git/git/blob/v2.21.0/editor.c#L101 (introduced in
> https://github.com/git/git/commit/abfb04d0c7#diff-cdeec438beb851e450b94a11db9ab7edR89)
> 
> So maybe we should do the same here, i.e.
> 
> 	fputs("\r\033[K", stderr);

Oh, that would be nice (and not only here, but it could have made the
changes in 'sg/overlong-progress-fix' a bit simpler as well).
Unfortunately, however, it only works on non-dumb terminals (note the
'!is_terminal_dumb()' call in the preceeding condition), while rebase
hasn't had such a limitation on the terminal yet.

> Ciao,
> Dscho
> >  			*end_of_arg = '\0';
> >  			res = do_exec(r, arg);
> >  			*end_of_arg = saved;
> > --
> > 2.21.0.1181.g24122a4251