fsck improvements

* fsck: Check if annex.numcopies is satisfied.
* fsck: Verify the sha1 of files when the SHA1 backend is used.
* fsck: Verify the size of files when the WORM backend is used.
* fsck: Allow specifying individual files to fsk if fscking everything
  is not desired.
* fsck: Fix bug, introduced in 0.04, in detection of unused data.

1 files changed, 34 insertions, 0 deletions

diff --git a/doc/walkthrough.mdwn b/doc/walkthrough.mdwn
index d6c0214ff..7effb5317 100644
--- a/doc/walkthrough.mdwn
+++ b/doc/walkthrough.mdwn
@@ -276,3 +276,37 @@ significantly for really big files. To make SHA1 the detault, just
 add something like this to `.gitattributes`:
 
 	* git-annex-backend=SHA1
+
+## fsck: verifying your data
+
+You can use the fsck subcommand to check for problems in your data.
+What can be checked depends on the [[backend|backends]] you've used to store
+the data. For example, when you use the SHA1 backend, fsck will verify that
+the checksums of your files are good. Fsck also checks that the annex.numcopies
+setting is satisfied for all files, and it warns about any dangling values
+in `.git/annex/objects/`. 
+
+	# git annex fsck
+	fsck  (checking for unused data...) (checking files...) ok
+
+Fsck checks the entire repository for problems by default. But you can
+also specify the files to check.
+This is particularly useful if you're using sha1 and don't want to spend
+a long time checksumming everything.
+
+	# git annex fsck my_cool_big_file
+	fsck my_cool_big_file (checksum..) ok
+
+## fsck: When things go wrong
+
+Fsck never deletes possibly bad data; instead it will be moved to
+`.git/annex/bad/` for you to review. Here is a sample of what fsck
+might say about a badly messed up annex:
+
+	# git annex fsck
+	fsck  (checking for unused data...) 
+	  Some annexed data is no longer pointed to by any files in the repository.
+	  If this data is no longer needed, it can be removed using git-annex dropkey:
+	    WORM:1289672605:3:file
+	(checking files...)
+