guix build: Add '--with-git-url'.

* guix/scripts/build.scm (%not-equal): New variable.
(evaluate-git-replacement-specs): Use it instead of local variable
'not-equal'.
(transform-package-source-git-url): New procedure.
(%transformations): Add 'with-git-url'.
(%transformation-options, show-transformation-options-help): Add
'--with-git-url'.
* tests/scripts-build.scm ("options->transformation, with-git-url"):
New test.

1 files changed, 23 insertions, 11 deletions

diff --git a/doc/guix.texi b/doc/guix.texi
index 5bbd0ee7f0..139a09d1bc 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -7780,22 +7780,18 @@ must be compatible.  If @var{replacement} is somehow incompatible with
 @var{package}, then the resulting package may be unusable.  Use with
 care!
 
-@item --with-branch=@var{package}=@var{branch}
+@item --with-git-url=@var{package}=@var{url}
 @cindex Git, using the latest commit
 @cindex latest commit, building
-Build @var{package} from the latest commit of @var{branch}.  The @code{source}
-field of @var{package} must be an origin with the @code{git-fetch} method
-(@pxref{origin Reference}) or a @code{git-checkout} object; the repository URL
-is taken from that @code{source}.  Git sub-modules of the repository are
-fetched, recursively.
+Build @var{package} from the latest commit of the @code{master} branch of the
+Git repository at @var{url}.
 
-For instance, the following command builds @code{guile-sqlite3} from the
-latest commit of its @code{master} branch, and then builds @code{guix} (which
-depends on it) and @code{cuirass} (which depends on @code{guix}) against this
-specific @code{guile-sqlite3} build:
+For example, the following commands builds the GNU C Library (glibc) straight
+from its Git repository instead of building the currently-packaged release:
 
 @example
-guix build --with-branch=guile-sqlite3=master cuirass
+guix build glibc \
+  --with-git-url=glibc=git://sourceware.org/git/glibc.git
 @end example
 
 @cindex continuous integration
@@ -7809,6 +7805,22 @@ Checkouts are kept in a cache under @file{~/.cache/guix/checkouts} to speed up
 consecutive accesses to the same repository.  You may want to clean it up once
 in a while to save disk space.
 
+@item --with-branch=@var{package}=@var{branch}
+Build @var{package} from the latest commit of @var{branch}.  The @code{source}
+field of @var{package} must be an origin with the @code{git-fetch} method
+(@pxref{origin Reference}) or a @code{git-checkout} object; the repository URL
+is taken from that @code{source}.  Git sub-modules of the repository are
+fetched, recursively.
+
+For instance, the following command builds @code{guile-sqlite3} from the
+latest commit of its @code{master} branch, and then builds @code{guix} (which
+depends on it) and @code{cuirass} (which depends on @code{guix}) against this
+specific @code{guile-sqlite3} build:
+
+@example
+guix build --with-branch=guile-sqlite3=master cuirass
+@end example
+
 @item --with-commit=@var{package}=@var{commit}
 This is similar to @code{--with-branch}, except that it builds from
 @var{commit} rather than the tip of a branch.  @var{commit} must be a valid