progress: add sparse mode to force 100% complete message

Add new start_sparse_progress() and start_delayed_sparse_progress()
constructors and "sparse" flag to struct progress.

Teach stop_progress() to force a 100% complete progress message before
printing the final "done" message when "sparse" is set.

Calling display_progress() for every item in a large set can
be expensive.  If callers try to filter this for performance
reasons, such as emitting every k-th item, progress would
not reach 100% unless they made a final call to display_progress()
with the item count before calling stop_progress().

Now this is automatic when "sparse" is set.

Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

progress.c

@@ -34,6 +34,7 @@ struct progress {
 	uint64_t total;
 	unsigned last_percent;
 	unsigned delay;
+	unsigned sparse;
 	struct throughput *throughput;
 	uint64_t start_ns;
 };
@@ -194,7 +195,7 @@ int display_progress(struct progress *progress, uint64_t n)
 }
 
 static struct progress *start_progress_delay(const char *title, uint64_t total,
-					     unsigned delay)
+					     unsigned delay, unsigned sparse)
 {
 	struct progress *progress = malloc(sizeof(*progress));
 	if (!progress) {
@@ -208,6 +209,7 @@ static struct progress *start_progress_delay(const char *title, uint64_t total,
 	progress->last_value = -1;
 	progress->last_percent = -1;
 	progress->delay = delay;
+	progress->sparse = sparse;
 	progress->throughput = NULL;
 	progress->start_ns = getnanotime();
 	set_progress_signal();
@@ -216,16 +218,46 @@ static struct progress *start_progress_delay(const char *title, uint64_t total,
 
 struct progress *start_delayed_progress(const char *title, uint64_t total)
 {
-	return start_progress_delay(title, total, 2);
+	return start_progress_delay(title, total, 2, 0);
 }
 
 struct progress *start_progress(const char *title, uint64_t total)
 {
-	return start_progress_delay(title, total, 0);
+	return start_progress_delay(title, total, 0, 0);
+}
+
+/*
+ * Here "sparse" means that the caller might use some sampling criteria to
+ * decide when to call display_progress() rather than calling it for every
+ * integer value in[0 .. total).  In particular, the caller might not call
+ * display_progress() for the last value in the range.
+ *
+ * When "sparse" is set, stop_progress() will automatically force the done
+ * message to show 100%.
+ */
+struct progress *start_sparse_progress(const char *title, uint64_t total)
+{
+	return start_progress_delay(title, total, 0, 1);
+}
+
+struct progress *start_delayed_sparse_progress(const char *title,
+					       uint64_t total)
+{
+	return start_progress_delay(title, total, 2, 1);
+}
+
+static void finish_if_sparse(struct progress *progress)
+{
+	if (progress &&
+	    progress->sparse &&
+	    progress->last_value != progress->total)
+		display_progress(progress, progress->total);
 }
 
 void stop_progress(struct progress **p_progress)
 {
+	finish_if_sparse(*p_progress);
+
 	stop_progress_msg(p_progress, _("done"));
 }
 

progress.h

@@ -6,7 +6,10 @@ struct progress;
 void display_throughput(struct progress *progress, uint64_t total);
 int display_progress(struct progress *progress, uint64_t n);
 struct progress *start_progress(const char *title, uint64_t total);
+struct progress *start_sparse_progress(const char *title, uint64_t total);
 struct progress *start_delayed_progress(const char *title, uint64_t total);
+struct progress *start_delayed_sparse_progress(const char *title,
+					       uint64_t total);
 void stop_progress(struct progress **progress);
 void stop_progress_msg(struct progress **progress, const char *msg);