The usual way to trigger a remote helper is to use the "::" syntax from:
87422439d1 (Allow specifying the remote helper in the url, 2009-11-18).
Doing:
git config remote.origin.url hg::https://example.com/repo
will run "git-remote-hg origin https://example.com/repo". Or you can
use the fallback handling from 25d5cc488a (Pass unknown protocols to
external protocol handlers, 2009-12-09):
git config remote.origin.url "foo://bar"
which will run "git-remote-foo origin foo://bar".
But there's a third way, from c578f51d52 (Add a config option for
remotes to specify a foreign vcs, 2009-11-18):
git config remote.origin.vcs foo
git config remote.origin.url bar
which will run "git-remote-foo origin bar". This is mostly redundant
with the other methods, except that it is supposed to allow you to run
without a URL at all. So:
git config remote.origin.vcs foo
would run "git-remote-foo origin" with no extra URL parameter (under the
assumption that the helper somehow knows how to access the remote repo).
However, this mode has been broken since 25d5cc488a, shortly after it
was added! That commit taught the transport code to always look at the
URL string to parse off the "foo::" bits, meaning it would always
segfault in the no-url case. You can see that with:
git -c remote.foo.vcs=bar fetch foo
Nobody seems to have noticed in the almost 15 years since, so presumably
it's not a well-used feature. And without that, arguably the whole
remote.*.vcs feature could be removed entirely, as it isn't offering
anything you couldn't do with the "helper::" syntax. But it _does_ work
if you have a URL, and it has been advertised in the documentation for
all that time. So we shouldn't just remove it without warning.
Likewise, even if we were going to deprecate it, we should avoid
breaking it in the meantime. Since there are no tests for it at all,
let's add a few basic ones:
- this syntax doesn't work well with "git clone" (another point
against it versus "helper::"). But we can use "clone -c" to set up
the config manually, passing the URL as usual to clone. This does
work, though note that I had to use --no-local in the test to avoid
broken interactions between the local code and the helper. In the
real world this would be a non-issue, since the remote URL would
generally not also be a local Git repo!
- likewise, we should be able to set up the config manually and fetch
into a repository. This also works.
- we can simulate a vcs that has no URL support by stuffing the remote
path into another environment variable. This should work, but
doesn't (it hits the segfault mentioned above).
In the first two cases, I took the extra step of checking GIT_TRACE
output to confirm that we actually ran the helper (since the URL is a
valid Git repo, the clone/fetch would appear to work even if we
didn't use the helper at all!).
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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