[bug#58433] [PATCH 0/2] Accept tags in the 'commit' field of <channel>

[bug#58433] [PATCH 0/2] Accept tags in the 'commit' field of <channel>

[Ludovic Courtès]

Hi!

This change lets us pass tags to ‘guix time-machine’ and ‘guix pull’,
as in:

  guix time-machine --commit=v1.2.0 -- describe

At last!

Thoughts?

Ludo’.

Ludovic Courtès (2):
  git: 'update-cached-checkout' returns the commit ID when given a tag.
  channels: Interpret the 'commit' field of channel as a tag or commit.

 doc/guix.texi     | 23 +++++++++++++++++++++--
 guix/channels.scm |  2 +-
 guix/git.scm      | 15 +++++++++------
 guix/inferior.scm |  2 +-
 tests/git.scm     | 32 +++++++++++++++++++++++++++++++-
 5 files changed, 63 insertions(+), 11 deletions(-)


base-commit: 5d5bc072059f514394afdaccfcc72cdb282d7ce2
-- 
2.38.0

[bug#58433] [PATCH 1/2] git: 'update-cached-checkout' returns the commit ID when given a tag.

[Ludovic Courtès]

Previously, starting with commit
efa578ecaece67366b4b0e2266de7c2faaa4ae54, 'update-cached-checkout' would
return the OID of the annotated tag the tag points to.  With this change
it returns the OID of the commit object in all cases.

* guix/git.scm (resolve-reference): In the 'tag' case, call
'tag-target-id' and 'tag-lookup' when OID designates an annotated tag.
* tests/git.scm ("update-cached-checkout, tag"): New test.
---
 guix/git.scm  | 15 +++++++++------
 tests/git.scm | 32 +++++++++++++++++++++++++++++++-
 2 files changed, 40 insertions(+), 7 deletions(-)

diff --git a/guix/git.scm b/guix/git.scm
index d7fd320f50..0220fe1068 100644
--- a/guix/git.scm
+++ b/guix/git.scm
@@ -271,12 +271,15 @@ (define (resolve-reference repository ref)
                   ;; There's no such tag, so it must be a commit ID.
                   (resolve `(commit . ,str)))))))
       (('tag    . tag)
-       (let ((oid (reference-name->oid repository
-                                       (string-append "refs/tags/" tag))))
-         ;; OID may point to a "tag" object, but it can also point directly
-         ;; to a "commit" object, as surprising as it may seem.  Return that
-         ;; object, whatever that is.
-         (object-lookup repository oid))))))
+       (let* ((oid (reference-name->oid repository
+                                        (string-append "refs/tags/" tag)))
+              (obj (object-lookup repository oid)))
+         ;; OID may designate an "annotated tag" object or a "commit" object.
+         ;; Return the commit object in both cases.
+         (if (= OBJ-TAG (object-type obj))
+             (object-lookup repository
+                            (tag-target-id (tag-lookup repository oid)))
+             obj))))))
 
 (define (switch-to-ref repository ref)
   "Switch to REPOSITORY's branch, commit or tag specified by REF.  Return the
diff --git a/tests/git.scm b/tests/git.scm
index ca59d2a33e..9c944d65b1 100644
--- a/tests/git.scm
+++ b/tests/git.scm
@@ -22,8 +22,12 @@ (define-module (test-git)
   #:use-module (guix git)
   #:use-module (guix tests git)
   #:use-module (guix build utils)
+  #:use-module ((guix utils) #:select (call-with-temporary-directory))
   #:use-module (srfi srfi-1)
-  #:use-module (srfi srfi-64))
+  #:use-module (srfi srfi-64)
+  #:use-module (srfi srfi-71)
+  #:use-module (ice-9 popen)
+  #:use-module (ice-9 textual-ports))
 
 ;; Test the (guix git) tools.
 
@@ -239,4 +243,30 @@ (define-module (test-git)
         (tag "v1.1" "Release 1.1"))
     (remote-refs directory #:tags? #t)))
 
+(unless (which (git-command)) (test-skip 1))
+(test-assert "update-cached-checkout, tag"
+  (call-with-temporary-directory
+   (lambda (cache)
+     (with-temporary-git-repository directory
+         '((add "a.txt" "A")
+           (commit "First commit")
+           (tag "v1.0" "release-1.0")
+           (branch "develop")
+           (checkout "develop")
+           (add "b.txt" "B")
+           (commit "Second commit")
+           (tag "v1.1" "release-1.1"))
+       (let ((directory commit relation
+                        (update-cached-checkout directory
+                                                #:ref '(tag . "v1.1")
+                                                #:cache-directory cache))
+             (head   (let* ((pipe (open-pipe* OPEN_READ (git-command)
+                                              "-C" directory
+                                              "rev-parse" "HEAD"))
+                            (str  (get-string-all pipe)))
+                       (close-pipe pipe)
+                       (string-trim-right str))))
+         ;; COMMIT should be the ID of the commit object, not that of the tag.
+         (string=? commit head))))))
+
 (test-end "git")
-- 
2.38.0

[bug#58433] [PATCH 2/2] channels: Interpret the 'commit' field of channel as a tag or commit.

[Ludovic Courtès]

Previously the 'commit' field would always be interpreted as a commit
ID.  This change adds flexibility, allowing for things like:

  guix time-machine --commit=v1.2.0 -- describe

* guix/channels.scm (channel-reference): Use 'tag-or-commit' rather than 'commit'.
* guix/inferior.scm (channel-full-commit): Likewise.
* doc/guix.texi (Invoking guix pull): Document it.
(Invoking guix time-machine): Likewise.
---
 doc/guix.texi     | 23 +++++++++++++++++++++--
 guix/channels.scm |  2 +-
 guix/inferior.scm |  2 +-
 3 files changed, 23 insertions(+), 4 deletions(-)

diff --git a/doc/guix.texi b/doc/guix.texi
index 14592142dd..4c24600f04 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -4631,7 +4631,7 @@ but it supports the following options:
 @itemx --branch=@var{branch}
 Download code for the @code{guix} channel from the specified @var{url}, at the
 given @var{commit} (a valid Git commit ID represented as a hexadecimal
-string), or @var{branch}.
+string or the name of a tag), or @var{branch}.
 
 @cindex @file{channels.scm}, configuration file
 @cindex configuration file for channels
@@ -4783,6 +4783,25 @@ of Guix to be used is defined by a commit or by a channel
 description file created by @command{guix describe}
 (@pxref{Invoking guix describe}).
 
+Let's assume that you want to travel to those days of November 2020 when
+version 1.2.0 of Guix was released and, once you're there, run the
+@command{guile} of that time:
+
+@example
+guix time-machine --commit=v1.2.0 -- \
+  environment -C --ad-hoc guile -- guile
+@end example
+
+The command above fetches Guix@tie{}1.2.0 and runs its @command{guix
+environment} command to spawn an environment in a container running
+@command{guile} (@command{guix environment} has since been subsumed by
+@command{guix shell}; @pxref{Invoking guix shell}).  It's like driving a
+DeLorean@footnote{If you don't know what a DeLorean is, consider
+traveling back to the 1980's.}!  The first @command{guix time-machine}
+invocation can be expensive: it may have to download or even build a
+large number of packages; the result is cached though and subsequent
+commands targeting the same commit are almost instantaneous.
+
 The general syntax is:
 
 @example
@@ -4799,7 +4818,7 @@ this revision are the same as for @command{guix pull} (@pxref{Invoking guix pull
 @itemx --branch=@var{branch}
 Use the @code{guix} channel from the specified @var{url}, at the
 given @var{commit} (a valid Git commit ID represented as a hexadecimal
-string), or @var{branch}.
+string or the name of a tag), or @var{branch}.
 
 @item --channels=@var{file}
 @itemx -C @var{file}
diff --git a/guix/channels.scm b/guix/channels.scm
index f1c23c17fb..d84228c47e 100644
--- a/guix/channels.scm
+++ b/guix/channels.scm
@@ -248,7 +248,7 @@ (define (channel-reference channel)
 'latest-repository-commit'."
   (match (channel-commit channel)
     (#f      `(branch . ,(channel-branch channel)))
-    (commit  `(commit . ,(channel-commit channel)))))
+    (commit  `(tag-or-commit . ,(channel-commit channel)))))
 
 (define sexp->channel-introduction
   (match-lambda
diff --git a/guix/inferior.scm b/guix/inferior.scm
index cbb3c0a36e..2fe34ca0dc 100644
--- a/guix/inferior.scm
+++ b/guix/inferior.scm
@@ -835,7 +835,7 @@ (define (channel-full-commit channel)
         (branch (channel-branch channel)))
     (if (and commit (commit-id? commit))
         commit
-        (let* ((ref (if commit `(commit . ,commit) `(branch . ,branch)))
+        (let* ((ref (if commit `(tag-or-commit . ,commit) `(branch . ,branch)))
                (cache commit relation
                      (update-cached-checkout (channel-url channel)
                                              #:ref ref
-- 
2.38.0

[bug#58433] [PATCH 0/2] Accept tags in the 'commit' field of <channel>

[Christopher Baines]

[-- Attachment #1: Type: text/plain, Size: 270 bytes --]


Ludovic Courtès <ludo@gnu.org> writes:

> This change lets us pass tags to ‘guix time-machine’ and ‘guix pull’,
> as in:
>
>   guix time-machine --commit=v1.2.0 -- describe
>
> At last!
>
> Thoughts?

This sounds good to me :)

Thanks,

Chris

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 987 bytes --]

bug#58433: [PATCH 0/2] Accept tags in the 'commit' field of <channel>

[Ludovic Courtès]

Hi,

Christopher Baines <mail@cbaines.net> skribis:

> Ludovic Courtès <ludo@gnu.org> writes:
>
>> This change lets us pass tags to ‘guix time-machine’ and ‘guix pull’,
>> as in:
>>
>>   guix time-machine --commit=v1.2.0 -- describe
>>
>> At last!
>>
>> Thoughts?
>
> This sounds good to me :)

Pushed, thanks for taking a look!

  f36522416e * channels: Interpret the 'commit' field of channel as a tag or commit.
  46f7011591 * git: 'update-cached-checkout' returns the commit ID when given a tag.

Ludo’.