repack: make '--quiet' disable progress

While testing some ideas in 'git repack', I ran it with '--quiet' and
discovered that some progress output was still shown. Specifically, the
output for writing the multi-pack-index showed the progress.

The 'show_progress' variable in cmd_repack() is initialized with
isatty(2) and is not modified at all by the '--quiet' flag. The
'--quiet' flag modifies the po_args.quiet option which is translated
into a '--quiet' flag for the 'git pack-objects' child process. However,
'show_progress' is used to directly send progress information to the
multi-pack-index writing logic which does not use a child process.

The fix here is to modify 'show_progress' to be false if po_opts.quiet
is true, and isatty(2) otherwise. This new expectation simplifies a
later condition that checks both.

This is difficult to test because the isatty(2) already prevents the
progess indicators from appearing when we redirect stderr to a file.

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>

builtin/repack.c

@@ -612,7 +612,7 @@ int cmd_repack(int argc, const char **argv, const char *prefix)
 	struct tempfile *refs_snapshot = NULL;
 	int i, ext, ret;
 	FILE *out;
-	int show_progress = isatty(2);
+	int show_progress;
 
 	/* variables to be filled by option parsing */
 	int pack_everything = 0;
@@ -725,6 +725,8 @@ int cmd_repack(int argc, const char **argv, const char *prefix)
 
 	prepare_pack_objects(&cmd, &po_args);
 
+	show_progress = !po_args.quiet && isatty(2);
+
 	strvec_push(&cmd.args, "--keep-true-parents");
 	if (!pack_kept_objects)
 		strvec_push(&cmd.args, "--honor-pack-keep");
@@ -926,7 +928,7 @@ int cmd_repack(int argc, const char **argv, const char *prefix)
 			}
 			strbuf_release(&buf);
 		}
-		if (!po_args.quiet && show_progress)
+		if (show_progress)
 			opts |= PRUNE_PACKED_VERBOSE;
 		prune_packed_objects(opts);