[bug#48667] [PATCH] doc: Expound on how to specify the version of a package.

[Xinglu Chen]

* doc/guix.texi (package Reference): Describe how packages that lack a release
or are pinned to an unreleased version should specify the ‘version’ field.
Add documentation for the ‘git-version’ procedure.
---
Changes since v1:
* Remove the case for “version 0”.

* Use @var{} instead of @code{} when appropriate, and @lisp instead of
  @example.

* Be more specific about what to set COMMIT to.  Git/Mercurial and
  SVN/Bzr should be handled differently.

 doc/guix.texi | 26 +++++++++++++++++++++++++-
 1 file changed, 25 insertions(+), 1 deletion(-)

diff --git a/doc/guix.texi b/doc/guix.texi
index e8b0485f78..9338136ebe 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -89,6 +89,7 @@ Copyright @copyright{} 2020 Jonathan Brielmaier@*
 Copyright @copyright{} 2020 Edgar Vincent@*
 Copyright @copyright{} 2021 Maxime Devos@*
 Copyright @copyright{} 2021 B. Wilson@*
+Copyright @copyright{} 2021 Xinglu Chen@*
 
 Permission is granted to copy, distribute and/or modify this document
 under the terms of the GNU Free Documentation License, Version 1.3 or
@@ -6651,7 +6652,21 @@ This is the data type representing a package recipe.
 The name of the package, as a string.
 
 @item @code{version}
-The version of the package, as a string.
+The version of the package, as a string.  If there are no releases of
+the package, or a unreleased version is desired, the version should
+contain @samp{@var{VERSION}-@var{REVISION}.@var{COMMIT}}.  @var{VERSION}
+is the version of the package, and @var{REVISION} is the revision of the
+Guix package (@code{0} if it is a new package).  Whenever the package is
+updated to a newer version the revision should also be bumped to reflect
+the fact that package has been updated.  If the fetch method for the
+package is @code{git-fetch} or @code{hg-fetch} (@pxref{origin
+Reference}), @var{COMMIT} should be the @dfn{commit} or @dfn{changeset}
+corresponding to the version, it should only contain 7 characters.  If
+the fetch method is @code{git-fetch}, there is the @code{git-version}
+procedure (see below) that makes it easier to specify the version.
+Packages which use @code{svn-fetch} or @code{bzr-fetch} should set
+@var{COMMIT} to the same value as the @code{revision} field in
+@code{svn-reference} or @code{bzr-reference}.
 
 @item @code{source}
 An object telling how the source code for the package should be
@@ -6757,6 +6772,15 @@ automatically corrected.
 @end table
 @end deftp
 
+@deffn {Scheme Procedure} git-version @var{VERSION} @var{REVISION} @var{COMMIT}
+Return the version string for packages using @code{git-fetch}.
+
+@lisp
+(git-version "0.2.3" "0" "93818c936ee7e2f1ba1b315578bde363a7d43d05")
+@result{} "0.2.3-0.93818c9"
+@end lisp
+@end deffn
+
 @deffn {Scheme Syntax} this-package
 When used in the @emph{lexical scope} of a package field definition, this
 identifier resolves to the package being defined.

base-commit: 3f2a4b098039bd374c76d524223de3c6c475f23e
-- 
2.31.1