update-index: do not die too early in a read-only repository.

diff --git a/Documentation/git-rev-parse.txt b/Documentation/git-rev-parse.txt
index ed938aafb0f7043131489a79e197f1c266cf9607..4041a1607081ee6e8d93065c67fc72a513c20b17 100644 (file)
--- a/Documentation/git-rev-parse.txt
+++ b/Documentation/git-rev-parse.txt
@@ -152,6 +152,18 @@ blobs contained in a commit.
   used immediately following a ref name and the ref must have an
   existing log ($GIT_DIR/logs/<ref>).
 
+* A ref followed by the suffix '@' with an ordinal specification
+  enclosed in a brace pair (e.g. '\{1\}', '\{15\}') to specify
+  the n-th prior value of that ref.  For example 'master@\{1\}'
+  is the immediate prior value of 'master' while 'master@\{5\}'
+  is the 5th prior value of 'master'. This suffix may only be used
+  immediately following a ref name and the ref must have an existing
+  log ($GIT_DIR/logs/<ref>).
+
+* You can use the '@' construct with an empty ref part to get at a
+  reflog of the current branch. For example, if you are on the
+  branch 'blabla', then '@\{1\}' means the same as 'blabla@\{1\}'.
+
 * A suffix '{caret}' to a revision parameter means the first parent of
   that commit object.  '{caret}<n>' means the <n>th parent (i.e.
   'rev{caret}'
@@ -239,14 +251,21 @@ of `r1` and `r2` and is defined as
 It it the set of commits that are reachable from either one of
 `r1` or `r2` but not from both.
 
-Here are a few examples:
+Two other shorthands for naming a set that is formed by a commit
+and its parent commits exists.  `r1{caret}@` notation means all
+parents of `r1`.  `r1{caret}!` includes commit `r1` but excludes
+its all parents.
+
+Here are a handful examples:
 
    D                A B D
    D F              A B C D F
-   ^A G                    B D
+   ^A G             B D
    ^A F             B C F
    G...I            C D F G I
-   ^B G I          C D F G I
+   ^B G I           C D F G I
+   F^@              A B C
+   F^! H            D F H
 
 Author
 ------