[PATCH v2] Documentation: Document how to get links with git am

[Linus Walleij <linus.walleij@linaro.org>]

This adds Kees' clever apply hook to the kernel documentation so
it can be easily references when needed.

Cc: Kees Cook <keescook@chromium.org>
Link: https://lists.linuxfoundation.org/pipermail/ksummit-discuss/2019-July/006608.html
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
---
ChangeLog v1->v2:
- Make the document part of maintainer/configure-git.rst
- Did not try to separate out to a standalone script file, the thing
  needs to come with other command line interaction anyway
---
 Documentation/maintainer/configure-git.rst | 30 ++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/Documentation/maintainer/configure-git.rst b/Documentation/maintainer/configure-git.rst
index 78bbbb0d2c84..80ae5030a590 100644
--- a/Documentation/maintainer/configure-git.rst
+++ b/Documentation/maintainer/configure-git.rst
@@ -32,3 +32,33 @@ You may also like to tell ``gpg`` which ``tty`` to use (add to your shell rc fil
 ::
 
 	export GPG_TTY=$(tty)
+
+
+Creating commit links to lore.kernel.org
+----------------------------------------
+
+The web site http://lore.kernel.org is meant as a grand archive of all mail
+list traffic concerning or influencing the kernel development. Storing archives
+of patches here is a recommended practice, and when a maintainer applies a
+patch to a subsystem tree, it is a good idea to provide a Link: tag with a
+reference back to the lore archive so that people that browse the commit
+history can find related discussions and rationale behind a certain change.
+The link tag will look like this:
+
+    Link: https://lore.kernel.org/r/<message-id>
+
+This can be configured to happen automatically any time you issue ``git am``
+by adding the following hook into your git:
+
+.. code-block:: none
+
+	$ git config am.messageid true
+	$ cat >.git/hooks/applypatch-msg <<'EOF'
+	#!/bin/sh
+	. git-sh-setup
+	perl -pi -e 's|^Message-Id:\s*<?([^>]+)>?$|Link: https://lore.kernel.org/r/$1|g;' "$1"
+	test -x "$GIT_DIR/hooks/commit-msg" &&
+		exec "$GIT_DIR/hooks/commit-msg" ${1+"$@"}
+	:
+	EOF
+	$ chmod a+x .git/hooks/applypatch-msg
-- 
2.23.0