From: Derrick Stolee <redacted>

The start_delayed_progress() method is a preferred way to show
optional progress to users as it ignores steps that take less
than two seconds. However, this makes testing unreliable as tests
expect to be very fast.

In addition, users may want to decrease or increase this time
interval depending on their preferences for terminal noise.

Create the GIT_PROGRESS_DELAY environment variable to control
the delay set during start_delayed_progress(). Set the value
in some tests to guarantee their output remains consistent.

Helped-by: Jeff King [off-list ref]
Signed-off-by: Derrick Stolee <redacted>
---
 Documentation/git.txt   | 4 ++++
 progress.c              | 8 +++++++-
 t/t5318-commit-graph.sh | 4 ++--
 t/t6500-gc.sh           | 3 +--
 4 files changed, 14 insertions(+), 5 deletions(-)

diff --git a/Documentation/git.txt b/Documentation/git.txt
index 9b82564d1a..1c420da208 100644
--- a/Documentation/git.txt
+++ b/Documentation/git.txt

@@ -544,6 +544,10 @@ other
 	a pager.  See also the `core.pager` option in
 	linkgit:git-config[1].
 
+`GIT_PROGRESS_DELAY`::
+	A number controlling how many seconds to delay before showing
+	optional progress indicators. Defaults to 2.
+
 `GIT_EDITOR`::
 	This environment variable overrides `$EDITOR` and `$VISUAL`.
 	It is used by several Git commands when, on interactive mode,

diff --git a/progress.c b/progress.c
index 0063559aab..4ad1a3c6eb 100644
--- a/progress.c
+++ b/progress.c

@@ -14,6 +14,7 @@
 #include "strbuf.h"
 #include "trace.h"
 #include "utf8.h"
+#include "config.h"
 
 #define TP_IDX_MAX      8
 

@@ -269,7 +270,12 @@ 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, 0);
+	static int delay_in_secs = -1;
+
+	if (delay_in_secs < 0)
+		delay_in_secs = git_env_ulong("GIT_PROGRESS_DELAY", 2);
+
+	return start_progress_delay(title, total, delay_in_secs, 0);
 }

diff --git a/t/t6500-gc.sh b/t/t6500-gc.sh
index c0f04dc6b0..7f79eedd1c 100755
--- a/t/t6500-gc.sh
+++ b/t/t6500-gc.sh

@@ -103,9 +103,8 @@ test_expect_success 'auto gc with too many loose objects does not attempt to cre
 '
 
 test_expect_success 'gc --no-quiet' '
-	git -c gc.writeCommitGraph=true gc --no-quiet >stdout 2>stderr &&
+	GIT_PROGRESS_DELAY=0 git -c gc.writeCommitGraph=true gc --no-quiet >stdout 2>stderr &&
 	test_must_be_empty stdout &&
-	test_line_count = 1 stderr &&