protocol: introduce protocol extension mechanisms

diff --git a/Documentation/merge-options.txt b/Documentation/merge-options.txt
index 30808a01e7657164618c18182704768e2df0d37e..4e323043017deee83d547e52e7797dd61a02cd5d 100644 (file)
--- a/Documentation/merge-options.txt
+++ b/Documentation/merge-options.txt
@@ -39,7 +39,7 @@ set to `no` at the beginning of them.
 
 --ff-only::
        Refuse to merge and exit with a non-zero status unless the
-       current `HEAD` is already up-to-date or the merge can be
+       current `HEAD` is already up to date or the merge can be
        resolved as a fast-forward.
 
 --log[=<n>]::
@@ -117,3 +117,11 @@ ifndef::git-pull[]
        reporting.
 
 endif::git-pull[]
+
+--allow-unrelated-histories::
+       By default, `git merge` command refuses to merge histories
+       that do not share a common ancestor.  This option can be
+       used to override this safety when merging histories of two
+       projects that started their lives independently. As that is
+       a very rare occasion, no configuration variable to enable
+       this by default exists and will not be added.