build-system: Add 'channel-build-system'.

* gnu/ci.scm (channel-build-system, channel-source->package): Remove.
* gnu/packages/package-management.scm (channel-source->package): New
procedure, moved from (gnu ci).
* guix/build-system/channel.scm: New file, with code moved from (gnu ci).
* doc/guix.texi (Build Systems): Document it.

1 files changed, 9 insertions, 0 deletions

diff --git a/doc/guix.texi b/doc/guix.texi
index 9a6a5c307d..5dab9cf169 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -9568,6 +9568,15 @@ with @code{build-expression->derivation} (@pxref{Derivations,
 @code{build-expression->derivation}}).
 @end defvr
 
+@defvr {Scheme Variable} channel-build-system
+This variable is exported by @code{(guix build-system channel)}.
+
+This build system is meant primarily for internal use.  It requires two
+arguments, @code{#:commit} and @code{#:source}, and builds a Guix
+instance from that channel, in the same way @command{guix time-machine}
+would do it (@pxref{Channels}).
+@end defvr
+
 @node Build Phases
 @section Build Phases