[PATCH] Documentation: clarify diff.external limitations

[Anders Melchiorsen <mail@cup.kalibalik.dk>]

The diff.external examples pass a flag to gnu-diff, but that is not
actually supported.

Without the flag, diff will still complain about an extra operand
because git is passing 7 parameters to the external command.

Both of these are fixed by suggesting a diff-wrapper and pointing to
the description of the parameters passed.

Signed-off-by: Anders Melchiorsen <mail@cup.kalibalik.dk>
---
 Documentation/config.txt     |   10 ++++++----
 Documentation/git-config.txt |    2 +-
 2 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/Documentation/config.txt b/Documentation/config.txt
index 798b551..1a13abc 100644
--- a/Documentation/config.txt
+++ b/Documentation/config.txt
@@ -92,7 +92,7 @@ Example
 
 	# Our diff algorithm
 	[diff]
-		external = "/usr/local/bin/gnu-diff -u"
+		external = /usr/local/bin/diff-wrapper
 		renames = true
 
 	[branch "devel"]
@@ -563,9 +563,11 @@ diff.autorefreshindex::
 diff.external::
 	If this config variable is set, diff generation is not
 	performed using the internal diff machinery, but using the
-	given command.  Note: if you want to use an external diff
-	program only on a subset of your files, you might want to
-	use linkgit:gitattributes[5] instead.
+	given command.  Can be overridden with the `GIT_EXTERNAL_DIFF'
+	environment variable.  The command is called with parameters
+	as described under "git Diffs" in linkgit:git[1].  Note: if
+	you want to use an external diff program only on a subset of
+	your files, you	might want to use linkgit:gitattributes[5] instead.
 
 diff.renameLimit::
 	The number of files to consider when performing the copy/rename
diff --git a/Documentation/git-config.txt b/Documentation/git-config.txt
index 697824c..28e1861 100644
--- a/Documentation/git-config.txt
+++ b/Documentation/git-config.txt
@@ -222,7 +222,7 @@ Given a .git/config like this:
 
 	; Our diff algorithm
 	[diff]
-		external = "/usr/local/bin/gnu-diff -u"
+		external = /usr/local/bin/diff-wrapper
 		renames = true
 
 	; Proxy settings
-- 
1.5.4.3