progress: break too long progress bar lines

Some of the recently added progress indicators have quite long titles,
which might be even longer when translated to some languages, and when
they are shown while operating on bigger repositories, then the
progress bar grows longer than the default 80 column terminal width.

When the progress bar exceeds the width of the terminal it gets
line-wrapped, and after that the CR at the end doesn't return to the
beginning of the progress bar, but to the first column of its last
line.  Consequently, the first line of the previously shown progress
bar is not overwritten by the next, and we end up with a bunch of
truncated progress bar lines scrolling past:

  $ LANG=es_ES.UTF-8 git commit-graph write
  Encontrando commits para commit graph entre los objetos empaquetados:   2% (1599
  Encontrando commits para commit graph entre los objetos empaquetados:   3% (1975
  Encontrando commits para commit graph entre los objetos empaquetados:   4% (2633
  Encontrando commits para commit graph entre los objetos empaquetados:   5% (3292
  [...]

Prevent this by breaking progress bars after the title once they
exceed the width of the terminal, so the counter and optional
percentage and throughput, i.e. all changing parts, are on the last
line.  Subsequent updates will from then on only refresh the changing
parts, but not the title, and it will look like this:

  $ LANG=es_ES.UTF-8 ~/src/git/git commit-graph write
  Encontrando commits para commit graph entre los objetos empaquetados:
    100% (6584502/6584502), listo.
  Calculando números de generación de commit graph: 100% (824705/824705), listo.
  Escribiendo commit graph en 4 pasos: 100% (3298820/3298820), listo.

Note that the number of columns in the terminal is cached by
term_columns(), so this might not kick in when it should when a
terminal window is resized while the operation is running.
Furthermore, this change won't help if the terminal is so narrow that
the counters don't fit on one line, but I would put this in the "If it
hurts, don't do it" box.

Signed-off-by: SZEDER Gábor <szeder.dev@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

progress.c

@@ -8,11 +8,12 @@
  * published by the Free Software Foundation.
  */
 
-#include "git-compat-util.h"
+#include "cache.h"
 #include "gettext.h"
 #include "progress.h"
 #include "strbuf.h"
 #include "trace.h"
+#include "utf8.h"
 
 #define TP_IDX_MAX      8
 
@@ -37,6 +38,8 @@ struct progress {
 	struct throughput *throughput;
 	uint64_t start_ns;
 	struct strbuf counters_sb;
+	int title_len;
+	int split;
 };
 
 static volatile sig_atomic_t progress_update;
@@ -115,8 +118,24 @@ static void display(struct progress *progress, uint64_t n, const char *done)
 			size_t clear_len = counters_sb->len < last_count_len ?
 					last_count_len - counters_sb->len + 1 :
 					0;
-			fprintf(stderr, "%s: %s%*s", progress->title,
-				counters_sb->buf, (int) clear_len, eol);
+			size_t progress_line_len = progress->title_len +
+						counters_sb->len + 2;
+			int cols = term_columns();
+
+			if (progress->split) {
+				fprintf(stderr, "  %s%*s", counters_sb->buf,
+					(int) clear_len, eol);
+			} else if (!done && cols < progress_line_len) {
+				clear_len = progress->title_len + 1 < cols ?
+					    cols - progress->title_len : 0;
+				fprintf(stderr, "%s:%*s\n  %s%s",
+					progress->title, (int) clear_len, "",
+					counters_sb->buf, eol);
+				progress->split = 1;
+			} else {
+				fprintf(stderr, "%s: %s%*s", progress->title,
+					counters_sb->buf, (int) clear_len, eol);
+			}
 			fflush(stderr);
 		}
 		progress_update = 0;
@@ -220,6 +239,8 @@ static struct progress *start_progress_delay(const char *title, uint64_t total,
 	progress->throughput = NULL;
 	progress->start_ns = getnanotime();
 	strbuf_init(&progress->counters_sb, 0);
+	progress->title_len = utf8_strwidth(title);
+	progress->split = 0;
 	set_progress_signal();
 	return progress;
 }