etc: Add tempel snippets.

* etc/snippets/tempel/scheme-mode: New file.
* etc/snippets/tempel/text-mode: New file.
* etc/snippets/scheme-mode: Moved from here...
* etc/snippets/yas/scheme-mode: ... to here.
* etc/snippets/text-mode: Moved from here...
* etc/snippets/yas/text-mode: ... to here.
* doc/contributing.texi ("The Perfect Setup"): Adjust yasnippet setup
accordingly.  Add tempel setup.

Signed-off-by: Liliana Marie Prikler <liliana.prikler@gmail.com>

doc/contributing.texi

@@ -320,15 +320,25 @@ s-expression, etc.
 @cindex reducing boilerplate
 We also provide templates for common git commit messages and package
 definitions in the @file{etc/snippets} directory.  These templates can
-be used with @url{https://joaotavora.github.io/yasnippet/, YASnippet} to
-expand short trigger strings to interactive text snippets.  You may want
-to add the snippets directory to the @var{yas-snippet-dirs} variable in
+be used to expand short trigger strings to interactive text snippets. If
+you use @url{https://joaotavora.github.io/yasnippet/, YASnippet}, you
+may want to add the @file{etc/snippets/yas} snippets directory to the
+@var{yas-snippet-dirs} variable.  If you use
+@url{https://github.com/minad/tempel/, Tempel}, you may want to add the
+@file{etc/snippets/tempel/*} path to the @var{tempel-path} variable in
 Emacs.
 
 @lisp
 ;; @r{Assuming the Guix checkout is in ~/src/guix.}
+;; @r{Yasnippet configuration}
 (with-eval-after-load 'yasnippet
-  (add-to-list 'yas-snippet-dirs "~/src/guix/etc/snippets"))
+  (add-to-list 'yas-snippet-dirs "~/src/guix/etc/snippets/yas"))
+;; @r{Tempel configuration}
+(with-eval-after-load 'tempel
+   ;; Ensure tempel-path is a list -- it may also be a string.
+   (unless (listp 'tempel-path)
+     (setq tempel-path (list tempel-path)))
+   (add-to-list 'tempel-path "~/src/guix/etc/snippets/tempel/*"))
 @end lisp
 
 The commit message snippets depend on @url{https://magit.vc/, Magit} to

etc/snippets/tempel/scheme-mode

@@ -0,0 +1,80 @@
+-*- mode: lisp-data -*-
+
+scheme-mode
+
+(package...
+ "(define-public " (s name)
+ n> "(package"
+ n  > "(name \"" (s name) "\")"
+ n  > "(version \"" p "\")"
+ n  > "(source origin...)"
+ n  > "(build-system " (p "gnu") "-build-system)"
+ n  > "(home-page \"" p "\")"
+ n  > "(synopsis \"" p "\")"
+ n  > "(description \"" p "\")"
+ n  > "(license license:" (p "unknown") ")))" n)
+
+(origin...
+ "(origin"
+ n> "(method " (p "url-fetch" method) ")"
+ n> "(uri " (cl-case (and method (intern method))
+              ('git-fetch "git-reference...")
+              ('svn-fetch "svn-reference...")
+              ('hg-fetch  "hg-reference...")
+              ('cvs-fetch "cvs-reference...")
+              ('bzr-fetch "bzr-reference...")
+              (t          "\"https://...\""))
+ ")"
+ n>
+ (cl-case (and method (intern method))
+   ('git-fetch
+    (insert "(file-name (git-file-name name version))")
+    (newline)
+    (indent-according-to-mode))
+   ('hg-fetch
+    (insert "(file-name (hg-file-name name version))")
+    (newline)
+    (indent-according-to-mode))
+   ('svn-fetch
+    (insert "(file-name (string-append name \"-\" version \"-checkout\"))")
+    (newline)
+    (indent-according-to-mode))
+   ('cvs-fetch
+    (insert "(file-name (string-append name \"-\" version \"-checkout\"))")
+    (newline)
+    (indent-according-to-mode))
+   ('bzr-fetch
+    (insert "(file-name (string-append name \"-\" version \"-checkout\"))")
+    (newline)
+    (indent-according-to-mode))
+   (t          ""))
+ > "(sha256"
+ n > "(base32 \""
+ ;; hash of an empty directory
+ (p "0sjjj9z1dhilhpc8pq4154czrb79z9cm044jvn75kxcjv6v5l2m5") "\")))")
+
+(git-reference...
+ "(git-reference"
+ n> "(url \"" p "\")"
+ n> "(commit \"" p "\"))")
+
+(svn-reference...
+ "(svn-reference"
+ n> "(url \"" p "\")"
+ n> "(revision \"" p "\"))")
+
+(cvs-reference...
+ "(cvs-reference"
+ n> "(root-directory \"" p "\")"
+ n> "(module \"" p "\")"
+ n> "(revision \"" p "\"))")
+
+(hg-reference...
+ "(hg-reference"
+ n> "(url \"" p "\")"
+ n> "(changeset \"" p "\"))")
+
+(bzr-reference...
+ "(bzr-reference"
+ n> "(url \"" p "\")"
+ n> "(revision \"" p "\"))")

etc/snippets/tempel/text-mode

@@ -0,0 +1,101 @@
+-*- mode: lisp-data -*-
+
+text-mode :when (and (fboundp 'git-commit-mode) (git-commit-mode))
+
+(add\ 
+ "gnu: Add "
+ (p
+  (with-temp-buffer
+    (magit-git-wash #'magit-diff-wash-diffs
+      "diff" "--staged")
+    (goto-char (point-min))
+    (when (re-search-forward "\\+(define-public \\(\\S-+\\)" nil 'noerror)
+      (match-string-no-properties 1)))
+  var ) "." n n
+ "* " (car (magit-staged-files)) " (" (s var ) "): New variable.")
+
+(remove\ 
+ "gnu: Remove "
+ (p (with-temp-buffer
+      (magit-git-wash #'magit-diff-wash-diffs
+        "diff" "--staged")
+      (goto-char (point-min))
+      (when (re-search-forward "\\-(define-public \\(\\S-+\\)" nil 'noerror)
+        (match-string-no-properties 1)))
+    var) "." n n
+ "* " (car (magit-staged-files)) " (" (s var) "): Delete variable.")
+
+(rename\ 
+ "gnu: "
+ (p (with-temp-buffer
+      (magit-git-wash #'magit-diff-wash-diffs
+        "diff" "--staged")
+      (beginning-of-buffer)
+      (when (search-forward "-(define-public " nil 'noerror)
+        (thing-at-point 'sexp 'no-properties)))
+    prev-var)
+ ": Rename package to "
+ (p (with-temp-buffer
+      (magit-git-wash #'magit-diff-wash-diffs
+        "diff" "--staged")
+      (beginning-of-buffer)
+      (when (search-forward "+(define-public " nil 'noerror)
+        (thing-at-point 'sexp 'no-properties)))
+    new-var) "." n n
+ "* " (car (magit-staged-files)) " (" (s prev-var) "): Define in terms of" n
+ "'deprecated-package'." n
+ "(" (s new-var) "): New variable, formerly known as \"" (s prev-var) "\".")
+
+(update\ 
+ "gnu: "
+ (p (with-temp-buffer
+      (magit-git-wash #'magit-diff-wash-diffs
+        "diff" "--staged")
+      (goto-char (point-min))
+      (when (re-search-forward "^[ ]*(define-public \\(\\S-+\\)" nil 'noerror)
+        (match-string-no-properties 1)))
+    var)
+ ": Update to "
+ (p (with-temp-buffer
+      (magit-git-wash #'magit-diff-wash-diffs
+        "diff" "--staged")
+      (goto-char (point-min))
+      (search-forward "name" nil 'noerror)
+      (search-forward "+" nil 'noerror)   ; first change
+      (when (and (search-forward "version " nil 'noerror)
+                 (looking-at-p "\""))
+        (let ((end (save-excursion (search-forward "\")" nil 'noerror))))
+          (when end
+            (forward-char)
+            (buffer-substring-no-properties (point) (- end 2))))))
+    version) "." n n
+ "* " (car (magit-staged-files)) " (" (s var) "): Update to " (s version) "."
+ (mapconcat (lambda (file) (concat "* " file)) (cdr (magit-staged-files))) n)
+
+(addcl\ 
+ "gnu: Add cl-"
+ (p (replace-regexp-in-string
+     "^cl-" "" (with-temp-buffer
+                 (magit-git-wash #'magit-diff-wash-diffs
+                   "diff" "--staged")
+                 (beginning-of-buffer)
+                 (when (search-forward "+(define-public " nil 'noerror)
+                   (replace-regexp-in-string
+                    "^sbcl-" ""
+                    (thing-at-point 'sexp 'no-properties)))))
+    var) "." n n
+ "* " (car (magit-staged-files))
+ " (cl-" (s var)  ", ecl-" (s var) ", sbcl-" (s var) "): New variables.")
+
+(https\ 
+ "gnu: "
+ (p (with-temp-buffer
+      (magit-git-wash #'magit-diff-wash-diffs
+        "diff" "--staged")
+      (goto-char (point-min))
+      (when (re-search-forward "^[ ]*(define-public \\(\\S-+\\)" nil 'noerror)
+        (match-string-no-properties 1)))
+    var)
+ ": Use HTTPS home page." n n
+ "* " (car (magit-staged-files)) " (" (s var) ")[home-page]: Use HTTPS." n
+ (mapconcat (lambda (file) (concat "* " file)) (cdr (magit-staged-files))) n)