Add support for url aliases in config files

This allows users with different preferences for access methods to the
same remote repositories to rewrite each other's URLs by pattern
matching across a large set of similiarly set up repositories to each
get the desired access.

For example, if you don't have a kernel.org account, you might want
settings like:

[url "git://git.kernel.org/pub/"]
      insteadOf = master.kernel.org:/pub

Then, if you give git a URL like:

  master.kernel.org:/pub/scm/linux/kernel/git/linville/wireless-2.6.git

it will act like you gave it:

  git://git.kernel.org/pub/scm/linux/kernel/git/linville/wireless-2.6.git

and you can cut-and-paste pull requests in email without fixing them
by hand, for example.

Signed-off-by: Daniel Barkalow <barkalow@iabervon.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

2 files changed, 35 insertions, 0 deletions

diff --git a/Documentation/config.txt b/Documentation/config.txt
index f2f6a774e0..298138917a 100644
--- a/Documentation/config.txt
+++ b/Documentation/config.txt
@@ -886,6 +886,18 @@ tar.umask::
 	archiving user's umask will be used instead.  See umask(2) and
 	linkgit:git-archive[1].
 
+url.<base>.insteadOf::
+	Any URL that starts with this value will be rewritten to
+	start, instead, with <base>. In cases where some site serves a
+	large number of repositories, and serves them with multiple
+	access methods, and some users need to use different access
+	methods, this feature allows people to specify any of the
+	equivalent URLs and have git automatically rewrite the URL to
+	the best alternative for the particular user, even for a
+	never-before-seen repository on the site. The effect of
+	having multiple `insteadOf` values from different
+	`<base>` match to an URL is undefined.
+
 user.email::
 	Your email address to be recorded in any newly created commits.
 	Can be overridden by the 'GIT_AUTHOR_EMAIL', 'GIT_COMMITTER_EMAIL', and
diff --git a/Documentation/urls.txt b/Documentation/urls.txt
index 81ac17f32a..fa34c67471 100644
--- a/Documentation/urls.txt
+++ b/Documentation/urls.txt
@@ -44,3 +44,26 @@ endif::git-clone[]
 ifdef::git-clone[]
 They are equivalent, except the former implies --local option.
 endif::git-clone[]
+
+
+If there are a large number of similarly-named remote repositories and
+you want to use a different format for them (such that the URLs you
+use will be rewritten into URLs that work), you can create a
+configuration section of the form:
+
+------------
+	[url "<actual url base>"]
+		insteadOf = <other url base>
+------------
+
+For example, with this:
+
+------------
+	[url "git://git.host.xz/"]
+		insteadOf = host.xz:/path/to/
+		insteadOf = work:
+------------
+
+a URL like "work:repo.git" or like "host.xz:/path/to/repo.git" will be
+rewritten in any context that takes a URL to be "git://git.host.xz/repo.git".
+