Respect channel directory for 'guix channel

[Kai Jellinghaus <kaij@j10-labs.com>]

I'm aware it's a bit of a special use-case but I'm wondering whether
it'd be possible to respect the channel directory (from .guix-channel)
when looking for self-build.\?
I've managed to get it somewhat working (by modifying
guix/channels.scm when looking for the file, and when applying
patches).
It does cause some unnecessary loads of .guix-channel, and my guille
knowledge hasn't progressed to the point that I could figure out how
to structure it differently.
There may also be some concern that this will fail too early for an
invalid 'guix channel? Not sure.

Here's a patch (not possible to apply as-is, sorry, the hashes will be off)
---
 guix-channel/guix/channels.scm | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/guix-channel/guix/channels.scm b/guix-channel/guix/channels.scm
index 34f63eb833..de9c239872 100644
--- a/guix-channel/guix/channels.scm
+++ b/guix-channel/guix/channels.scm
@@ -455,7 +455,10 @@ (define (dot-git? file stat)
     (when (guix-channel? channel)
       ;; Apply the relevant subset of PATCHES directly in CHECKOUT.  This is
       ;; safe to do because 'switch-to-ref' eventually does a hard reset.
-      (apply-patches checkout commit patches))
+      (apply-patches
+        (string-append checkout (channel-metadata-directory
+          (read-channel-metadata-from-source checkout)))
+        commit patches))

     (let* ((name     (url+commit->name (channel-url channel) commit))
            (checkout (add-to-store store name #t "sha256" checkout
@@ -717,7 +720,9 @@ (define name
     (symbol->string
      (channel-name (channel-instance-channel instance))))
   (define source
-    (channel-instance-checkout instance))
+    (string-append
+      (channel-instance-checkout instance)
+      (channel-metadata-directory (channel-instance-metadata instance))))
   (define commit
     (channel-instance-commit instance))

-- 
2.46.0