[PATCH] doc: remove mentions of .gitmodules !command syntax

[pvutov@imap.cc]

From: Petar Vutov <pvutov@imap.cc>

To mitigate CVE-2019-19604, the capability to configure
`git submodule update` to execute custom commands was
removed in v2.20.2.

The git-submodule documentation still mentions the now-unsupported
syntax, which is misleading.

Remove the leftover documentation.

Signed-off-by: Petar Vutov <pvutov@imap.cc>
---
 Documentation/git-submodule.txt | 6 ------
 1 file changed, 6 deletions(-)

diff --git a/Documentation/git-submodule.txt b/Documentation/git-submodule.txt
index 4d3ab6b9f9..b40ac72f75 100644
--- a/Documentation/git-submodule.txt
+++ b/Documentation/git-submodule.txt
@@ -163,12 +163,6 @@ checked out in the submodule.
 The following 'update' procedures are only available via the
 `submodule.<name>.update` configuration variable:
 
-	custom command;; arbitrary shell command that takes a single
-	    argument (the sha1 of the commit recorded in the
-	    superproject) is executed. When `submodule.<name>.update`
-	    is set to '!command', the remainder after the exclamation mark
-	    is the custom command.
-
 	none;; the submodule is not updated.
 
 If the submodule is not yet initialized, and you just want to use the
-- 
2.41.0