git-download: Add support for Git Large File Storage (LFS).

* guix/build/git.scm (git-fetch) [lfs?]: New argument, doc and setup code.
(git-fetch-with-fallback) [lfs?]: New argument.  Pass it to git-fetch.
* guix/git-download.scm (git-lfs-package): New procedure.
(git-fetch/in-band*): New procedure, made of the logic of git-fetch/in-band,
with new git-lfs specifics, with the following changes:
New #:git-lfs argument.
<inputs>: Remove labels.  Conditionally add git-lfs.
<build>: Read "git lfs?" environment
variable and pass its value to the #:lfs? argument of git-fetch-with-fallback.
Use INPUTS directly; update comment.
<gexp->derivation>: Add "git lfs?" to #:env-vars.
(git-fetch/in-band): Express in terms of git-fetch/in-band*.
(git-fetch/lfs): New procedure.
* doc/guix.texi (origin Reference): Document it.

Change-Id: I5b233b8642a7bdb8737b9d9b740e7254a89ccb25
Reviewed-by: Ludovic Courtès <ludo@gnu.org>

1 files changed, 7 insertions, 0 deletions

diff --git a/doc/guix.texi b/doc/guix.texi
index 9f06f1c325..8c78ff8c0c 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -8375,6 +8375,13 @@ hash @var{hash} of type @var{hash-algo} (a symbol).  Use @var{name} as
 the file name, or a generic name if @code{#f}.
 @end deffn
 
+@deffn {Procedure} git-fetch/lfs ref hash-algo hash
+This is a variant of the @code{git-fetch} procedure that supports the
+Git @acronym{LFS, Large File Storage} extension.  This may be useful to
+pull some binary test data to run the test suite of a package, for
+example.
+@end deffn
+
 @deftp {Data Type} git-reference
 This data type represents a Git reference for @code{git-fetch} to
 retrieve.