git-download: Rewrite 'git-predicate' using Guile-Git.

Fixes <https://bugs.gnu.org/27925>.

* guix/git-download.scm (files->directory-tree)
(directory-in-tree?): Remove.
(git-file-list): New procedures.
(git-predicate): Use it instead of opening a pipe to 'git'.  Remove
directory tree hack and rely exclusively on inode/device numbers.

guix/git-download.scm

@@ -1,5 +1,5 @@
 ;;; GNU Guix --- Functional package management for GNU
-;;; Copyright © 2014, 2015, 2016, 2017 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2014, 2015, 2016, 2017, 2018 Ludovic Courtès <ludo@gnu.org>
 ;;; Copyright © 2017 Mathieu Lirzin <mthl@gnu.org>
 ;;; Copyright © 2017 Christopher Baines <mail@cbaines.net>
 ;;;
@@ -19,7 +19,6 @@
 ;;; along with GNU Guix.  If not, see <http://www.gnu.org/licenses/>.
 
 (define-module (guix git-download)
-  #:use-module (guix build utils)
   #:use-module (guix gexp)
   #:use-module (guix store)
   #:use-module (guix monads)
@@ -27,9 +26,8 @@
   #:use-module (guix packages)
   #:use-module (guix modules)
   #:autoload   (guix build-system gnu) (standard-packages)
+  #:use-module (git)
   #:use-module (ice-9 match)
-  #:use-module (ice-9 popen)
-  #:use-module (ice-9 rdelim)
   #:use-module (ice-9 vlist)
   #:use-module (srfi srfi-1)
   #:export (git-reference
@@ -153,41 +151,31 @@ HASH-ALGO (a symbol).  Use NAME as the file name, or a generic name if #f."
 ;;; 'git-predicate'.
 ;;;
 
-(define (files->directory-tree files)
+(define (git-file-list directory)
-  "Return a tree of vhashes representing the directory listed in FILES, a list
+  "Return the list of files checked in in the Git repository at DIRECTORY.
-like '(\"a/b\" \"b/c/d\")."
+The result is similar to that of the 'git ls-files' command, except that it
-  (fold (lambda (file result)
+also includes directories, not just regular files.  The returned file names
-          (let loop ((file (string-split file #\/))
+are relative to DIRECTORY, which is not necessarily the root of the checkout."
-                     (result result))
+  (let* ((directory  (canonicalize-path directory))
-            (match file
+         (dot-git    (repository-discover directory))
-              ((_)
+         (top        (dirname dot-git))
-               result)
+         (repository (repository-open dot-git))
-              ((directory children ...)
+         (head       (repository-head repository))
-               (match (vhash-assoc directory result)
+         (oid        (reference-target head))
-                 (#f
+         (commit     (commit-lookup repository oid))
-                  (vhash-cons directory (loop children vlist-null)
+         (tree       (commit-tree commit))
-                              result))
+         (files      (tree-list tree)))
-                 ((_ . previous)
+    (repository-close! repository)
-                  ;; XXX: 'vhash-delete' is O(n).
+    (if (string=? top directory)
-                  (vhash-cons directory (loop children previous)
+        files
-                              (vhash-delete directory result)))))
+        (let ((relative (string-append
-              (()
+                         (string-drop directory
-               result))))
+                                      (+ 1 (string-length top)))
-        vlist-null
+                         "/")))
-        files))
+          (filter-map (lambda (file)
-
+                        (and (string-prefix? relative file)
-(define (directory-in-tree? tree directory)
+                             (string-drop file (string-length relative))))
-  "Return true if DIRECTORY, a string like \"a/b\", denotes a directory listed
+                      files)))))
-in TREE."
-  (let loop ((directory (string-split directory #\/))
-             (tree       tree))
-    (match directory
-      (()
-       #t)
-      ((head . tail)
-       (match (vhash-assoc head tree)
-         ((_ . sub-tree) (loop tail sub-tree))
-         (#f #f))))))
 
 (define (git-predicate directory)
   "Return a predicate that returns true if a file is part of the Git checkout
@@ -195,15 +183,7 @@ living at DIRECTORY.  Upon Git failure, return #f instead of a predicate.
 
 The returned predicate takes two arguments FILE and STAT where FILE is an
 absolute file name and STAT is the result of 'lstat'."
-  (let* ((pipe           (with-directory-excursion directory
+  (let* ((files  (git-file-list directory))
-                           (open-pipe* OPEN_READ "git" "ls-files")))
-         (files          (let loop ((lines '()))
-                           (match (read-line pipe)
-                             ((? eof-object?)
-                              (reverse lines))
-                             (line
-                              (loop (cons line lines))))))
-         (directory-tree (files->directory-tree files))
          (inodes (fold (lambda (file result)
                          (let ((stat
                                 (lstat (string-append directory "/"
@@ -211,27 +191,12 @@ absolute file name and STAT is the result of 'lstat'."
                            (vhash-consv (stat:ino stat) (stat:dev stat)
                                         result)))
                        vlist-null
-                               files))
+                       files)))
-
-         ;; Note: For this to work we must *not* call 'canonicalize-path' on
-         ;; DIRECTORY or we would get discrepancies of the returned lambda is
-         ;; called with a non-canonical file name.
-         (prefix-length  (+ 1 (string-length directory)))
-
-         (status         (close-pipe pipe)))
-    (and (zero? status)
     (lambda (file stat)
-           (match (stat:type stat)
+      ;; Comparing file names is always tricky business so we rely on inode
-             ('directory
+      ;; numbers instead.
-              (directory-in-tree? directory-tree
-                                  (string-drop file prefix-length)))
-             ((or 'regular 'symlink)
-              ;; Comparing file names is always tricky business so we rely on
-              ;; inode numbers instead
       (match (vhash-assv (stat:ino stat) inodes)
         ((_ . dev) (= dev (stat:dev stat)))
-                (#f        #f)))
+        (#f        #f)))))
-             (_
-              #f))))))
 
 ;;; git-download.scm ends here