Documentation: revamp git-cherry(1)

git-cherry(1)'s "description" section has never really managed to explain to me what the command does. It contains too much explanation of the algorithm instead of simply saying what goals it achieves, and too much terminology that we otherwise do not use (fork-point instead of merge-base). Try a much more concise approach: state what it finds out, why this is neat, and how the output is formatted, in a few short paragraphs. In return, provide much longer examples of how it fits into a "format-patch | am" based workflow, and how it compares to reading the same from git-log. Also carefully avoid using "merge" in a context where it does not mean something that comes from git-merge(1). Instead, say "apply" in an attempt to further link to patch workflow concepts. While there, also omit the language about _which_ upstream branch we treat as the default. I literally just learned that we support having several, so let's not confuse new users here, especially considering that git-config(1) does not document this. Prompted-by: a.huemer@commend.com on #git Signed-off-by: Thomas Rast <tr@thomasrast.ch> Signed-off-by: Junio C Hamano <gitster@pobox.com>
git-mirror · Nov 27, 2013 · 7c801fb · 7c801fb
1 parent ccba805
commit 7c801fb
Showing 1 changed file with 110 additions and 33 deletions.
diff --git a/Documentation/git-cherry.txt b/Documentation/git-cherry.txt
@@ -3,7 +3,7 @@ git-cherry(1)
 
 NAME
 ----
-git-cherry - Find commits not merged upstream
+git-cherry - Find commits yet to be applied to upstream
 
 SYNOPSIS
 --------
@@ -12,53 +12,130 @@ SYNOPSIS
 
 DESCRIPTION
 -----------
-The changeset (or "diff") of each commit between the fork-point and <head>
-is compared against each commit between the fork-point and <upstream>.
-The diffs are compared after removing any whitespace and line numbers.
+Determine whether there are commits in `<head>..<upstream>` that are
+equivalent to those in the range `<limit>..<head>`.
 
-Every commit that doesn't exist in the <upstream> branch
-has its id (sha1) reported, prefixed by a symbol.  The ones that have
-equivalent change already
-in the <upstream> branch are prefixed with a minus (-) sign, and those
-that only exist in the <head> branch are prefixed with a plus (+) symbol:
-
-               __*__*__*__*__> <upstream>
-              /
-    fork-point
-              \__+__+__-__+__+__-__+__> <head>
-
-
-If a <limit> has been given then the commits along the <head> branch up
-to and including <limit> are not reported:
-
-               __*__*__*__*__> <upstream>
-              /
-    fork-point
-              \__*__*__<limit>__-__+__> <head>
-
-
-Because 'git cherry' compares the changeset rather than the commit id
-(sha1), you can use 'git cherry' to find out if a commit you made locally
-has been applied <upstream> under a different commit id.  For example,
-this will happen if you're feeding patches <upstream> via email rather
-than pushing or pulling commits directly.
+The equivalence test is based on the diff, after removing whitespace
+and line numbers.  git-cherry therefore detects when commits have been
+"copied" by means of linkgit:git-cherry-pick[1], linkgit:git-am[1] or
+linkgit:git-rebase[1].
 
+Outputs the SHA1 of every commit in `<limit>..<head>`, prefixed with
+`-` for commits that have an equivalent in <upstream>, and `+` for
+commits that do not.
 
 OPTIONS
 -------
 -v::
-	Verbose.
+	Show the commit subjects next to the SHA1s.
 
 <upstream>::
-	Upstream branch to compare against.
-	Defaults to the first tracked remote branch, if available.
+	Upstream branch to search for equivalent commits.
+	Defaults to the upstream branch of HEAD.
 
 <head>::
 	Working branch; defaults to HEAD.
 
 <limit>::
 	Do not report commits up to (and including) limit.
 
+EXAMPLES
+--------
+
+Patch workflows
+~~~~~~~~~~~~~~~
+
+git-cherry is frequently used in patch-based workflows (see
+linkgit:gitworkflows[7]) to determine if a series of patches has been
+applied by the upstream maintainer.  In such a workflow you might
+create and send a topic branch like this:
+
+------------
+$ git checkout -b topic origin/master
+# work and create some commits
+$ git format-patch origin/master
+$ git send-email ... 00*
+------------
+
+Later, you can see whether your changes have been applied by saying
+(still on `topic`):
+
+------------
+$ git fetch  # update your notion of origin/master
+$ git cherry -v
+------------
+
+Concrete example
+~~~~~~~~~~~~~~~~
+
+In a situation where topic consisted of three commits, and the
+maintainer applied two of them, the situation might look like:
+
+------------
+$ git log --graph --oneline --decorate --boundary origin/master...topic
+* 7654321 (origin/master) upstream tip commit
+[... snip some other commits ...]
+* cccc111 cherry-pick of C
+* aaaa111 cherry-pick of A
+[... snip a lot more that has happened ...]
+| * cccc000 (topic) commit C
+| * bbbb000 commit B
+| * aaaa000 commit A
+|/
+o 1234567 branch point
+------------
+
+In such cases, git-cherry shows a concise summary of what has yet to
+be applied:
+
+------------
+$ git cherry origin/master topic
+- cccc000... commit C
++ bbbb000... commit B
+- aaaa000... commit A
+------------
+
+Here, we see that the commits A and C (marked with `-`) can be
+dropped from your `topic` branch when you rebase it on top of
+`origin/master`, while the commit B (marked with `+`) still needs to
+be kept so that it will be sent to be applied to `origin/master`.
+
+
+Using a limit
+~~~~~~~~~~~~~
+
+The optional <limit> is useful in cases where your topic is based on
+other work that is not in upstream.  Expanding on the previous
+example, this might look like:
+
+------------
+$ git log --graph --oneline --decorate --boundary origin/master...topic
+* 7654321 (origin/master) upstream tip commit
+[... snip some other commits ...]
+* cccc111 cherry-pick of C
+* aaaa111 cherry-pick of A
+[... snip a lot more that has happened ...]
+| * cccc000 (topic) commit C
+| * bbbb000 commit B
+| * aaaa000 commit A
+| * 0000fff (base) unpublished stuff F
+[... snip ...]
+| * 0000aaa unpublished stuff A
+|/
+o 1234567 merge-base between upstream and topic
+------------
+
+By specifying `base` as the limit, you can avoid listing commits
+between `base` and `topic`:
+
+------------
+$ git cherry origin/master topic base
+- cccc000... commit C
++ bbbb000... commit B
+- aaaa000... commit A
+------------
+
+
 SEE ALSO
 --------
 linkgit:git-patch-id[1]