rev-list: Introduce --quiet to avoid /dev/null redirects

Some uses of git-rev-list are to run it with --objects to see if
a range of objects between two or more commits is fully connected
or not.  In such a case the caller doesn't care about the actual
object names or hash hints so formatting this data only for it to
be dumped to /dev/null by a redirect is a waste of CPU time.  If
all the caller needs is the exit status then --quiet can be used
to bypass the commit and object formatting.

Signed-off-by: Shawn O. Pearce <spearce@spearce.org>

1 files changed, 9 insertions, 0 deletions

diff --git a/Documentation/git-rev-list.txt b/Documentation/git-rev-list.txt
index 4852804..989fbf3 100644
--- a/Documentation/git-rev-list.txt
+++ b/Documentation/git-rev-list.txt
@@ -20,6 +20,7 @@ SYNOPSIS
 	     [ \--not ]
 	     [ \--all ]
 	     [ \--stdin ]
+	     [ \--quiet ]
 	     [ \--topo-order ]
 	     [ \--parents ]
 	     [ \--timestamp ]
@@ -270,6 +271,14 @@ limiting may be applied.
 	In addition to the '<commit>' listed on the command
 	line, read them from the standard input.
 
+--quiet::
+
+	Don't print anything to standard output.  This form of
+	git-rev-list is primarly meant to allow the caller to
+	test the exit status to see if a range of objects is fully
+	connected (or not).  It is faster than redirecting stdout
+	to /dev/null as the output does not have to be formatted.
+
 --cherry-pick::
 
 	Omit any commit that introduces the same change as