* lisp/emacs-lisp/package-vc.el (package-vc-release-rev): Use new
signature.
* lisp/vc/vc-git.el (vc-git-last-change): Update signature
* lisp/vc/vc.el (vc-default-last-change): Update signature and use
'annotate-command'.
* lisp/emacs-lisp/package-vc.el (package-vc-archive-spec-alist):
Unmention :release-rev
(package-vc-desc->spec): Fall back on other archives if a
specification is missing.
(package-vc-main-file): Add new function, copying the behaviour of
elpa-admin.el.
(package-vc-generate-description-file): Use 'package-vc-main-file'.
(package-vc-unpack): Handle special value ':last-release'.
(package-vc-release-rev): Add new function using 'last-change'.
(package-vc-install): Pass ':last-release' as REV instead of a
release.
* lisp/vc/vc-git.el (vc-git-last-change): Add Git 'last-change'
implementation.
* lisp/vc/vc.el (vc-default-last-change): Add default 'last-change'
implementation.
This attempts to replicate the behaviour of elpa-admin.el's
"elpaa--get-last-release-commit".
* lisp/emacs-lisp/package-vc.el (package-vc-archive-spec-alist):
Document the feature.
(package-vc-unpack): Check for :vc-backend in both PKG-SPEC and the
archive specification data.
* lisp/emacs-lisp/package-vc.el (package-vc--archives-initialize): Add
new function, extending 'package--archives-initialize'.
(package-vc-install): Use new function.
(package-vc-link-directory): Use new function.
* lisp/emacs-lisp/package-vc.el (package-vc-archive-spec-alist):
Update docstring.
(package-vc-install): Use :release-rev if invoked with a prefix argument.
* lisp/emacs-lisp/package-vc.el (package-vc-guess-backend): New
function.
(package-vc-unpack): Use it.
(package-vc-sourced-packages-list): Use it.
(package-vc-install): Use it.
* lisp/emacs-lisp/package-vc.el (package-vc-build-documentation): Add
function to build a documentation file.
(package-vc-unpack-1): Use 'package-vc-build-documentation'.
* lisp/emacs-lisp/package-vc.el (package-vc-default-backend): Add new
option.
(package-vc-archive-spec-alist): Add new variable to store the
contents of 'elpa-packages' for each archive.
(pacakge-vc-desc->spec): Add function to query package specifications.
(package-vc--read-archive-data): Add a 'package-read-archive-hook'
implementation.
(package-vc--download-and-read-archives): Add a
'package-refresh-contents-hook' implementation.
(package-vc-main-file): Remove function.
(package-vc-generate-description-file): Use package specifications.
(package-vc-unpack-1): Adapt to previous changes.
(package-vc-unpack): Adapt to previous changes.
(package-vc-sourced-packages-list): Adapt to previous changes.
(package-vc-install): Adapt to previous changes.
* lisp/emacs-lisp/package.el (package-read-archive-hook): Allow
extending 'package-read-all-archive-contents' using a hook.
(package-read-all-archive-contents): Use 'package-read-archive-hook'.
(package-refresh-contents-hook): Allow extending
'package-refresh-contents' using a hook.
(package-refresh-contents): Use 'package-refresh-contents-hook'.
* lisp/emacs-lisp/package-vc.el (package-vc-unpack-1): Add new function.
(package-vc-unpack): Use 'package-vc-unpack-1'.
(package-vc-link-project): Add new command.
* lisp/emacs-lisp/package-vc.el (package-vc-unpack): Check if the
upstream data indicates a custom lisp directory.
* lisp/emacs-lisp/package.el (package--delete-directory): Adapt
accordingly.
* lisp/emacs-lisp/package-vc.el (package-vc-fetch): Rename to preserve
symmetry with 'package-install'.
(package-checkout): Follow the previous rename.
* lisp/emacs-lisp/package-vc.el (package-vc-repository-store): Add new
user option.
(package-vc-unpack): Use 'package-vc-repository-store'.
* lisp/emacs-lisp/package.el (package--delete-directory): Check and
handle source packages.
(package-delete): Invoke 'package--delete-directory' with an
additional argument.
* package-vc.el (package-vc-probable-repository-regexp): Rename to
'package-vc-heusitic-alist'.
(package-vc-heusitic-alist): Add support for multiple VC backends.
(package-vc-sourced-packages-list): Use 'package-vc-heusitic-alist'
