Update draft release notes

diff --git a/Documentation/git-merge-base.txt b/Documentation/git-merge-base.txt
index a9f677b8f2c4b46b8c00a2435675cf679ec30625..87842e33f8aebc7d27fa732af1de15f0e4175c07 100644 (file)
--- a/Documentation/git-merge-base.txt
+++ b/Documentation/git-merge-base.txt
@@ -11,6 +11,7 @@ SYNOPSIS
 [verse]
 'git merge-base' [-a|--all] <commit> <commit>...
 'git merge-base' [-a|--all] --octopus <commit>...
+'git merge-base' --is-ancestor <commit> <commit>
 'git merge-base' --independent <commit>...
 
 DESCRIPTION
@@ -23,23 +24,21 @@ that does not have any better common ancestor is a 'best common
 ancestor', i.e. a 'merge base'.  Note that there can be more than one
 merge base for a pair of commits.
 
-Unless `--octopus` is given, among the two commits to compute the merge
-base from, one is specified by the first commit argument on the command
-line; the other commit is a (possibly hypothetical) commit that is a merge
-across all the remaining commits on the command line.  As the most common
-special case, specifying only two commits on the command line means
-computing the merge base between the given two commits.
+OPERATION MODE
+--------------
+
+As the most common special case, specifying only two commits on the
+command line means computing the merge base between the given two commits.
+
+More generally, among the two commits to compute the merge base from,
+one is specified by the first commit argument on the command line;
+the other commit is a (possibly hypothetical) commit that is a merge
+across all the remaining commits on the command line.
 
 As a consequence, the 'merge base' is not necessarily contained in each of the
 commit arguments if more than two commits are specified. This is different
 from linkgit:git-show-branch[1] when used with the `--merge-base` option.
 
-OPTIONS
--------
--a::
---all::
-       Output all merge bases for the commits, instead of just one.
-
 --octopus::
        Compute the best common ancestors of all supplied commits,
        in preparation for an n-way merge.  This mimics the behavior
@@ -52,6 +51,18 @@ OPTIONS
        from any other.  This mimics the behavior of 'git show-branch
        --independent'.
 
+--is-ancestor::
+       Check if the first <commit> is an ancestor of the second <commit>,
+       and exit with status 0 if true, or with status 1 if not.
+       Errors are signaled by a non-zero status that is not 1.
+
+
+OPTIONS
+-------
+-a::
+--all::
+       Output all merge bases for the commits, instead of just one.
+
 DISCUSSION
 ----------
 
@@ -106,13 +117,26 @@ both '1' and '2' are merge-bases of A and B.  Neither one is better than
 the other (both are 'best' merge bases).  When the `--all` option is not given,
 it is unspecified which best one is output.
 
-Author
-------
-Written by Linus Torvalds <torvalds@osdl.org>
+A common idiom to check "fast-forward-ness" between two commits A
+and B is (or at least used to be) to compute the merge base between
+A and B, and check if it is the same as A, in which case, A is an
+ancestor of B.  You will see this idiom used often in older scripts.
+
+       A=$(git rev-parse --verify A)
+       if test "$A" = "$(git merge-base A B)"
+       then
+               ... A is an ancestor of B ...
+       fi
+
+In modern git, you can say this in a more direct way:
+
+       if git merge-base --is-ancestor A B
+       then
+               ... A is an ancestor of B ...
+       fi
+
+instead.
 
-Documentation
---------------
-Documentation by David Greaves, Junio C Hamano and the git-list <git@vger.kernel.org>.
 
 See also
 --------