Merge branch 'pb/doc-orig-head'

Document ORIG_HEAD a bit more.

* pb/doc-orig-head:
  git-rebase.txt: add a note about 'ORIG_HEAD' being overwritten
  revisions.txt: be explicit about commands writing 'ORIG_HEAD'
  git-merge.txt: mention 'ORIG_HEAD' in the Description
  git-reset.txt: mention 'ORIG_HEAD' in the Description
  git-cherry-pick.txt: do not use 'ORIG_HEAD' in example

Author: gitster

Documentation/git-cherry-pick.txt

@@ -219,7 +219,7 @@ again, this time exercising more care about matching up context lines.
 ------------
 $ git cherry-pick topic^             <1>
 $ git diff                           <2>
-$ git reset --merge ORIG_HEAD        <3>
+$ git cherry-pick --abort            <3>
 $ git cherry-pick -Xpatience topic^  <4>
 ------------
 <1> apply the change that would be shown by `git show topic^`.

Documentation/git-merge.txt

@@ -37,7 +37,8 @@ Then "`git merge topic`" will replay the changes made on the
 `topic` branch since it diverged from `master` (i.e., `E`) until
 its current commit (`C`) on top of `master`, and record the result
 in a new commit along with the names of the two parent commits and
-a log message from the user describing the changes.
+a log message from the user describing the changes. Before the operation,
+`ORIG_HEAD` is set to the tip of the current branch (`C`).
 
 ------------
 	  A---B---C topic

Documentation/git-rebase.txt

@@ -38,6 +38,13 @@ The current branch is reset to `<upstream>` or `<newbase>` if the
 `git reset --hard <upstream>` (or `<newbase>`). `ORIG_HEAD` is set
 to point at the tip of the branch before the reset.
 
+[NOTE]
+`ORIG_HEAD` is not guaranteed to still point to the previous branch tip
+at the end of the rebase if other commands that write that pseudo-ref
+(e.g. `git reset`) are used during the rebase. The previous branch tip,
+however, is accessible using the reflog of the current branch
+(i.e. `@{1}`, see linkgit:gitrevisions[7]).
+
 The commits that were previously saved into the temporary area are
 then reapplied to the current branch, one by one, in order. Note that
 any commits in `HEAD` which introduce the same textual changes as a commit

Documentation/git-reset.txt

@@ -49,7 +49,8 @@ section of linkgit:git-add[1] to learn how to operate the `--patch` mode.
 'git reset' [<mode>] [<commit>]::
 	This form resets the current branch head to `<commit>` and
 	possibly updates the index (resetting it to the tree of `<commit>`) and
-	the working tree depending on `<mode>`. If `<mode>` is omitted,
+	the working tree depending on `<mode>`. Before the operation, `ORIG_HEAD`
+	is set to the tip of the current branch. If `<mode>` is omitted,
 	defaults to `--mixed`. The `<mode>` must be one of the following:
 +
 --

Documentation/revisions.txt

@@ -49,7 +49,8 @@ characters and to avoid word splitting.
 `FETCH_HEAD` records the branch which you fetched from a remote repository
 with your last `git fetch` invocation.
 `ORIG_HEAD` is created by commands that move your `HEAD` in a drastic
-way, to record the position of the `HEAD` before their operation, so that
+way (`git am`, `git merge`, `git rebase`, `git reset`),
+to record the position of the `HEAD` before their operation, so that
 you can easily change the tip of the branch back to the state before you ran
 them.
 `MERGE_HEAD` records the commit(s) which you are merging into your branch