graph: add commit graph design document

diff --git a/Documentation/git-describe.txt b/Documentation/git-describe.txt
index c924c945ba8b79e578ddbb7598aa29fabcdf5887..e027fb8c4b8269bb2266ca98f87c9c18ca45fad3 100644 (file)
--- a/Documentation/git-describe.txt
+++ b/Documentation/git-describe.txt
@@ -3,14 +3,14 @@ git-describe(1)
 
 NAME
 ----
-git-describe - Describe a commit using the most recent tag reachable from it
-
+git-describe - Give an object a human readable name based on an available ref
 
 SYNOPSIS
 --------
 [verse]
 'git describe' [--all] [--tags] [--contains] [--abbrev=<n>] [<commit-ish>...]
 'git describe' [--all] [--tags] [--contains] [--abbrev=<n>] --dirty[=<mark>]
+'git describe' <blob>
 
 DESCRIPTION
 -----------
@@ -24,6 +24,12 @@ By default (without --all or --tags) `git describe` only shows
 annotated tags.  For more information about creating annotated tags
 see the -a and -s options to linkgit:git-tag[1].
 
+If the given object refers to a blob, it will be described
+as `<commit-ish>:<path>`, such that the blob can be found
+at `<path>` in the `<commit-ish>`, which itself describes the
+first commit in which this blob occurs in a reverse revision walk
+from HEAD.
+
 OPTIONS
 -------
 <commit-ish>...::
@@ -186,6 +192,14 @@ selected and output.  Here fewest commits different is defined as
 the number of commits which would be shown by `git log tag..input`
 will be the smallest number of commits possible.
 
+BUGS
+----
+
+Tree objects as well as tag objects not pointing at commits, cannot be described.
+When describing blobs, the lightweight tags pointing at blobs are ignored,
+but the blob is still described as <committ-ish>:<path> despite the lightweight
+tag being favorable.
+
 GIT
 ---
 Part of the linkgit:git[1] suite