diffdriver: New git-annex command, to make git external diff drivers work with annexed files.

Closes https://github.com/datalad/datalad/issues/18

1 files changed, 15 insertions, 0 deletions

diff --git a/doc/git-annex.mdwn b/doc/git-annex.mdwn
index f1404af46..7ccb36b5d 100644
--- a/doc/git-annex.mdwn
+++ b/doc/git-annex.mdwn
@@ -989,6 +989,21 @@ subdirectories).
   Merge conflicts between two files that are not annexed will not be
   automatically resolved.
 
+* `diffdriver`
+
+  This is an external git diff driver shim. Normally, when using `git diff`
+  with an external git driver, the symlinks to annexed files are not set up
+  right, so the external git driver cannot read them in order to perform
+  smart diffing of their contents. This command works around the problem,
+  by passing the fixed up files to the real external diff driver.
+
+  To use, just configure git to use "git-annex diffdriver -- cmd params --"
+  as the external diff command, where cmd is the real external diff
+  command you want to use, and params are any extra parameters to pass
+  to it. Note the trailing "--", which is required.
+
+  For example, set `GIT_EXTERNAL_DIFF=git-annex diffdriver -- j-c-diff --`
+
 * `remotedaemon`
 
   Detects when network remotes have received git pushes and fetches from them.