gnu: Add emacs-next.

Add `emacs-next' for building latest Emacs from git.

* gnu/packages/emacs.scm (emacs-next): New variable.
(emacs): make the autoload deletion snippet not fail when eshell/esh-groups.el
does not exist.  This enables reuse of the entire snippet field of `emacs' for
`emacs-next'.
* gnu/packages/patches/emacs27-exec-path.patch: New file.
* gnu/local.mk (dist_patch_DATA): Add the above patch file to it.

Signed-off-by: Ludovic Courtès <ludo@gnu.org>

1 files changed, 18 insertions, 0 deletions

diff --git a/gnu/packages/patches/emacs27-exec-path.patch b/gnu/packages/patches/emacs27-exec-path.patch
new file mode 100644
index 0000000000..418aa633a1
--- /dev/null
+++ b/gnu/packages/patches/emacs27-exec-path.patch
@@ -0,0 +1,18 @@
+Do not capture the build-time value of $PATH in the 'emacs' executable
+since this can noticeably increase the size of the closure of Emacs
+with things like GCC being referenced.
+
+(like emacs-exec-path.patch, but for Emacs 27)
+
+--- a/lisp/loadup.el
++++ b/lisp/loadup.el
+@@ -479,7 +479,8 @@ lost after dumping")))
+                         ((equal dump-mode "dump") "emacs")
+                         ((equal dump-mode "bootstrap") "emacs")
+                         ((equal dump-mode "pbootstrap") "bootstrap-emacs.pdmp")
+-                        (t (error "unrecognized dump mode %s" dump-mode)))))
++                        (t (error "unrecognized dump mode %s" dump-mode))))
++          (exec-path nil))
+       (message "Dumping under the name %s" output)
+       (condition-case ()
+           (delete-file output)