On VCS-independent ways of identifying commits, and why they are desirable.

No code changes.

2 files changed, 14 insertions, 0 deletions

diff --git a/admin/ChangeLog b/admin/ChangeLog
index 36a10fa5f30..111d6441518 100644
--- a/admin/ChangeLog
+++ b/admin/ChangeLog
@@ -1,3 +1,8 @@
+2014-01-16  Eric S. Raymond  <esr@thyrsus.com>
+
+	* notes/commits: Add a 'graph on VCS-independent ways of
+	identifying commits and the desirability thereof.
+
 2014-01-15  Paul Eggert  <eggert@cs.ucla.edu>
 
 	Fix copyright license notices for Adobe Unicode mapping files.
diff --git a/admin/notes/commits b/admin/notes/commits
index 2c6f80c56f0..6e2aabe5abc 100644
--- a/admin/notes/commits
+++ b/admin/notes/commits
@@ -45,6 +45,15 @@ Date: 	 Tue, 31 Mar 2009 12:21:20 +0900
     for modern source-control systems with a global log, it's better to
     have something like "Regenerate configure".
 
+(4) (Added in 2014) In commit comments, and ChangLog files, it is best
+    to use ways of identifying revisions that are not dependent on a
+    particular version control system.  (At time of writing Emacs is
+    about to move to its third VCS and another move in the future is
+    not impossible.)  An excellent way to identify commits is by
+    quoting their summary line.  Another is with an action stamp - an
+    RFC3339 date followed by ! followed by the committer's email - for
+    example, "2014-01-16T05:43:35Z!esr@thyrsus.com". Often, "my
+    previous commit" will suffice.
 
 Followup discussion:
 http://lists.gnu.org/archive/html/emacs-devel/2010-01/msg00897.html