Documentation: describe subject more precisely

The discussion of email subject throughout the documentation is
misleading; it indicates that the first line will always become
the subject.  In fact, the subject is generally all lines up until
the first full blank line.

This patch refines that, and makes more use of the concept of a
commit title, with the title being all text up to the first blank line.

Signed-off-by: Jeremy White <jwhite@codeweavers.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 7 insertions, 4 deletions

diff --git a/Documentation/git-format-patch.txt b/Documentation/git-format-patch.txt
index 04c7346e3e..6d43f56279 100644
--- a/Documentation/git-format-patch.txt
+++ b/Documentation/git-format-patch.txt
@@ -58,10 +58,13 @@ output, unless the `--stdout` option is specified.
 If `-o` is specified, output files are created in <dir>.  Otherwise
 they are created in the current working directory.
 
-By default, the subject of a single patch is "[PATCH] First Line" and
-the subject when multiple patches are output is "[PATCH n/m] First
-Line". To force 1/1 to be added for a single patch, use `-n`.  To omit
-patch numbers from the subject, use `-N`.
+By default, the subject of a single patch is "[PATCH] " followed by
+the concatenation of lines from the commit message up to the first blank
+line (see the DISCUSSION section of linkgit:git-commit[1]).
+
+When multiple patches are output, the subject prefix will instead be
+"[PATCH n/m] ".  To force 1/1 to be added for a single patch, use `-n`.
+To omit patch numbers from the subject, use `-N`.
 
 If given `--thread`, `git-format-patch` will generate `In-Reply-To` and
 `References` headers to make the second and subsequent patch mails appear