[PATCH v2] doc: mention that 'git submodule update' fetches missing commits

[Philippe Blain <levraiphilippeblain@gmail.com>]

'git submodule update' will fetch new commits from the submodule remote
if the SHA-1 recorded in the superproject is not found. This was not
mentioned in the documentation.

Helped-by: Junio C Hamano <gitster@pobox.com>
Helped-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Philippe Blain <levraiphilippeblain@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
Changes since v1 [4]:
- Added my signed-off, corrected my email address
  and shortened the title of the commit message
  (I had actually done that when I resent my patch in [1] using submitGit, 
  but this dit not add the "v2" prefix)
- Added Junio's suggestion [2] (which was applied in [3] on top of the original 
  submission [4] instead of the revised one [1]), and squashed
- Added Helped-by trailers
- Rebased on v2.23.0 (as was done for [3])

[1] https://public-inbox.org/git/0102016b72a55a7d-fb4ecdb7-9f2b-4204-b888-0000f209c3ff-000000@eu-west-1.amazonses.com/
[2] https://public-inbox.org/git/xmqq8sobdzul.fsf@gitster-ct.c.googlers.com/
[3] https://github.com/gitster/git/commits/pb/submodule-update-fetches
[4] https://public-inbox.org/git/0102016a2274c90f-3dbf792f-5b0a-4da4-ada0-9a163a14e68d-000000@eu-west-1.amazonses.com/

 Documentation/git-submodule.txt | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/Documentation/git-submodule.txt b/Documentation/git-submodule.txt
index 0ed5c24dc1..4beb569ae5 100644
--- a/Documentation/git-submodule.txt
+++ b/Documentation/git-submodule.txt
@@ -133,7 +133,8 @@ update [--init] [--remote] [-N|--no-fetch] [--[no-]recommend-shallow] [-f|--forc
 +
 --
 Update the registered submodules to match what the superproject
-expects by cloning missing submodules and updating the working tree of
+expects by cloning missing submodules, fetching missing commits
+in submodules and updating the working tree of
 the submodules. The "updating" can be done in several ways depending
 on command line options and the value of `submodule.<name>.update`
 configuration variable. The command line option takes precedence over
-- 
2.23.0