Re: [RFC/PATCH Second draft] Fast forward strategies allow, never, and only

From

Sverre Hvammen Johansen <hvammen@gmail.com>

Date

Mar 19, 2008, 06:20 UTC

Message-ID

<402c10cd0803182320k134116cas5f62389482f2650a@mail.gmail.com>

In-Reply-To

<m363vkvvzb.fsf@localhost.localdomain>

I have added some more documentation:

diff --git a/Documentation/git-merge.txt b/Documentation/git-merge.txt
index 2af33d8..5af5436 100644
--- a/Documentation/git-merge.txt
+++ b/Documentation/git-merge.txt
@@ -36,7 +36,7 @@ include::merge-options.txt[]
 <remote>::
        Other branch head merged into our branch.  You need at
        least one <remote>.  Specifying more than one <remote>
-       obviously means you are trying an Octopus.
+       usually means you are trying an Octopus.


 include::fast-forward-options.txt[]
@@ -133,6 +133,47 @@ merge (which is typically a fraction of the whole
tree), you can
 have local modifications in your working tree as long as they do
 not overlap with what the merge updates.

+If more than one commit are specified for the merge, git will try to
+reduce the number of commits (real parents) by eliminating commits
+than can be reached from other commits.  The commit message will
+reflect the actual commits specified but the merge strategy will be
+selected based on the real parents always including `HEAD`.  The real
+parents (only including `HEAD` if it is real) are the parents recorded
+in the merge commit object.
+
+The following shows master and three topic branches.  TopicB is based
+on TopicA, TopicA is previously branched off from master, and TopicC
+is based on the current `HEAD` of master:
+
+------------
+                    o---o---o  TopicB
+                   /
+          o---o---o  TopicA
+         /
+    o---o---o---o---o---o  master
+                         \
+                          o---o  TopicC
+------------
+
+A merger of master with TopicA, TopicB, and TopicC will select the
+merge strategy based on the three branches master, TopicB, and TopicC
+(TopicA is eliminated since it can be reached from TopicB).  TopicB
+and TopicC are the only real parents and are therefore the only
+parents recorded in the merge commit object:
+
+------------
+         % git co master
+         % git merge TopicA TopicB TopicC
+
+                    o---o---o  TopicB
+                   /         \
+          o---o---o  TopicA   \
+         /                     \
+    o---o---o---o---o---o       o  master
+                         \     /
+                          o---o  TopicC
+------------
+
 When there are conflicts, these things happen:

 1. `HEAD` stays the same.

On Tue, Mar 18, 2008 at 8:27 AM, Jakub Narebski <jnareb@gmail.com> wrote:
>  I'd mention here receive.denyNonFastForward option as a way to set
>  this globally for all branches, for public bare publishing
>  repositories; AFAIK for push and I think also for fetch.

The denyNonFastForward option have nothing to do with merges.  It only
applies to push on the server side.  A merge is not involved when
doing a push.

-- 
Sverre Hvammen Johansen