improve

1 files changed, 10 insertions, 5 deletions

diff --git a/doc/git-annex-diffdriver.mdwn b/doc/git-annex-diffdriver.mdwn
index 72e0faca3..3df61154e 100644
--- a/doc/git-annex-diffdriver.mdwn
+++ b/doc/git-annex-diffdriver.mdwn
@@ -9,14 +9,19 @@ git annex diffdriver `-- cmd --opts --`
 # DESCRIPTION
 
 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
+with an external diff driver, the symlinks to annexed files are not set up
+right, so the external diff 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 use this, you will need to have installed some git external diff driver
+command. This is not the regular diff command; it takes a git-specific
+input. See git's documentation of `GIT_EXTERNAL_DIFF` and
+gitattributes(5)'s documentation of external diff drivers.
+
+Configure git to use "git-annex diffdriver -- cmd params --"
+as the external diff driver, where cmd is the external diff
+driver you want it to run, 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 --`