add git annex view command

(And a vpop command, which is still a bit buggy.)

Still need to do vadd and vrm, though this also adds their documentation.

Currently not very happy with the view log data serialization. I had to
lose the TDFA regexps temporarily, so I can have Read/Show instances of
View. I expect the view log format will change in some incompatable way
later, probably adding last known refs for the parent branch to View
or something like that.

Anyway, it basically works, although it's a bit slow looking up the
metadata. The actual git branch construction is about as fast as it can be
using the current git plumbing.

This commit was sponsored by Peter Hogg.

1 files changed, 27 insertions, 0 deletions

diff --git a/doc/git-annex.mdwn b/doc/git-annex.mdwn
index 1b7271092..84cb55a43 100644
--- a/doc/git-annex.mdwn
+++ b/doc/git-annex.mdwn
@@ -313,6 +313,33 @@ subdirectories).
   from a remote computer.
   Note that this does not yet use HTTPS for security, so use with caution!
 
+* `view [field=value ...] [tag ...]`
+
+  Uses metadata to build a view branch of the files in the current branch,
+  and checks out the view branch. Only files in the current branch whose
+  metadata matches all the specified field values and tags will be
+  shown in the view.
+  
+  Multiple values for a metadata field can be specified, either by using
+  a glob (field="\*") or by listing each wanted value. 
+  
+  When multiple field values match, the view branch will have a
+  subdirectory for each value.
+
+* `vadd [field=value ...] [tag ...]`
+
+  Can be used when already in a view to add additional fields or tags
+  to the view.
+
+* `vrm [field=value ...] [tag ...]`
+
+  Can be used when already in a view to remove fields or tags from the
+  view.
+
+* `vpop`
+
+  Switches from the currently active view back to the previous view.
+
 # REPOSITORY SETUP COMMANDS
 
 * `init [description]`