builtin/describe: introduce --broken flag

git-describe tells you the version number you're at, or errors out, e.g.
when you run it outside of a repository, which may happen when downloading
a tar ball instead of using git to obtain the source code.

To keep this property of only erroring out, when not in a repository,
severe (submodule) errors must be downgraded to reporting them gently
instead of having git-describe error out completely.

To achieve that a flag '--broken' is introduced, which is in the same
vein as '--dirty' but uses an actual child process to check for dirtiness.
When that child dies unexpectedly, we'll append '-broken' instead of
'-dirty'.

Signed-off-by: Stefan Beller <sbeller@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 8 insertions, 3 deletions

diff --git a/Documentation/git-describe.txt b/Documentation/git-describe.txt
index 8755f3a..26f19d3 100644
--- a/Documentation/git-describe.txt
+++ b/Documentation/git-describe.txt
@@ -30,9 +30,14 @@ OPTIONS
 	Commit-ish object names to describe.  Defaults to HEAD if omitted.
 
 --dirty[=<mark>]::
-	Describe the working tree.
-	It means describe HEAD and appends <mark> (`-dirty` by
-	default) if the working tree is dirty.
+--broken[=<mark>]::
+	Describe the state of the working tree.  When the working
+	tree matches HEAD, the output is the same as "git describe
+	HEAD".  If the working tree has local modification "-dirty"
+	is appended to it.  If a repository is corrupt and Git
+	cannot determine if there is local modification, Git will
+	error out, unless `--broken' is given, which appends
+	the suffix "-broken" instead.
 
 --all::
 	Instead of using only the annotated tags, use any ref