t5505: fix "set-head --auto with ambiguous HEAD" test

When two or more branches point at the same commit and HEAD is
pointing at one of them, without the symref extension, there is no
way to remotely tell which one of these branches HEAD points at.
The test in question attempts to make sure that this situation is
diagnosed and results in a failure.

However, even if there _were_ a way to reliably tell which branch
the HEAD points at, "set-head --auto" would fail if there is no
remote tracking branch.  Make sure that this test does not fail
for that "wrong" reason.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
upload-pack.c: do not pass confusing cb_data to mark_our_ref()

The callee does not use cb_data, and the caller is an intermediate
function in a callchain that later wants to use the cb_data for its
own use.  Clarify the code by breaking the dataflow explicitly by
not passing cb_data down to mark_our_ref().

Signed-off-by: Junio C Hamano <gitster@pobox.com>
upload-pack: send symbolic ref information as capability

One long-standing flaw in the pack transfer protocol was that there
was no way to tell the other end which branch "HEAD" points at.
With a capability "symref=HEAD:refs/heads/master", let the sender to
tell the receiver what symbolic ref points at what ref.

This capability can be repeated more than once to represent symbolic
refs other than HEAD, such as "refs/remotes/origin/HEAD").

Add an infrastructure to collect symbolic refs, format them as extra
capabilities and put it on the wire.  For now, just send information
on the "HEAD" and nothing else.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
upload-pack: send non-HEAD symbolic refs

With the same mechanism as used to tell where "HEAD" points at to
the other end, we can tell the target of other symbolic refs as
well.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
connect.c: make parse_feature_value() static

Signed-off-by: Junio C Hamano <gitster@pobox.com>
connect: annotate refs with their symref information in get_remote_head()

By doing this, clients of upload-pack can now reliably tell what ref
a symbolic ref points at; the updated test in t5505 used to expect
failure due to the ambiguity and made sure we give diagnostics, but
we no longer need to be so pessimistic. Make sure we correctly learn
which branch HEAD points at from the other side instead.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
clone: test the new HEAD detection logic

Signed-off-by: Junio C Hamano <gitster@pobox.com>
http_get_file: style fixes

Besides being ugly, the extra parentheses are idiomatic for
suppressing compiler warnings when we are assigning within a
conditional. We aren't doing that here, and they just
confuse the reader.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
http_request: factor out curlinfo_strbuf

When we retrieve the content-type of an http response, curl
gives us a pointer to internal storage, which we then copy
into a strbuf. Let's factor out the get-and-copy routine,
which can be used for getting other curl info.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
http: refactor options to http_get_*

Over time, the http_get_strbuf function has grown several
optional parameters. We now have a bitfield with multiple
boolean options, as well as an optional strbuf for returning
the content-type of the response. And a future patch in this
series is going to add another strbuf option.

Treating these as separate arguments has a few downsides:

  1. Most call sites need to add extra NULLs and 0s for the
     options they aren't interested in.

  2. The http_get_* functions are actually wrappers around
     2 layers of low-level implementation functions. We have
     to pass these options through individually.

  3. The http_get_strbuf wrapper learned these options, but
     nobody bothered to do so for http_get_file, even though
     it is backed by the same function that does understand
     the options.

Let's consolidate the options into a single struct. For the
common case of the default options, we'll allow callers to
simply pass a NULL for the options struct.

The resulting code is often a few lines longer, but it ends
up being easier to read (and to change as we add new
options, since we do not need to update each call site).

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
http: hoist credential request out of handle_curl_result

When we are handling a curl response code in http_request or
in the remote-curl RPC code, we use the handle_curl_result
helper to translate curl's response into an easy-to-use
code. When we see an HTTP 401, we do one of two things:

  1. If we already had a filled-in credential, we mark it as
     rejected, and then return HTTP_NOAUTH to indicate to
     the caller that we failed.

  2. If we didn't, then we ask for a new credential and tell
     the caller HTTP_REAUTH to indicate that they may want
     to try again.

Rejecting in the first case makes sense; it is the natural
result of the request we just made. However, prompting for
more credentials in the second step does not always make
sense. We do not know for sure that the caller is going to
make a second request, and nor are we sure that it will be
to the same URL. Logically, the prompt belongs not to the
request we just finished, but to the request we are (maybe)
about to make.

In practice, it is very hard to trigger any bad behavior.
Currently, if we make a second request, it will always be to
the same URL (even in the face of redirects, because curl
handles the redirects internally). And we almost always
retry on HTTP_REAUTH these days. The one exception is if we
are streaming a large RPC request to the server (e.g., a
pushed packfile), in which case we cannot restart. It's
extremely unlikely to see a 401 response at this stage,
though, as we would typically have seen it when we sent a
probe request, before streaming the data.

This patch drops the automatic prompt out of case 2, and
instead requires the caller to do it. This is a few extra
lines of code, and the bug it fixes is unlikely to come up
in practice. But it is conceptually cleaner, and paves the
way for better handling of credentials across redirects.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
http: provide effective url to callers

When we ask curl to access a URL, it may follow one or more
redirects to reach the final location. We have no idea
this has happened, as curl takes care of the details and
simply returns the final content to us.

The final URL that we ended up with can be accessed via
CURLINFO_EFFECTIVE_URL. Let's make that optionally available
to callers of http_get_*, so that they can make further
decisions based on the redirection.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
http: update base URLs when we see redirects

If a caller asks the http_get_* functions to go to a
particular URL and we end up elsewhere due to a redirect,
the effective_url field can tell us where we went.

It would be nice to remember this redirect and short-cut
further requests for two reasons:

  1. It's more efficient. Otherwise we spend an extra http
     round-trip to the server for each subsequent request,
     just to get redirected.

  2. If we end up with an http 401 and are going to ask for
     credentials, it is to feed them to the redirect target.
     If the redirect is an http->https upgrade, this means
     our credentials may be provided on the http leg, just
     to end up redirected to https. And if the redirect
     crosses server boundaries, then curl will drop the
     credentials entirely as it follows the redirect.

However, it, it is not enough to simply record the effective
URL we saw and use that for subsequent requests. We were
originally fed a "base" url like:

   http://example.com/foo.git

and we want to figure out what the new base is, even though
the URLs we see may be:

     original: http://example.com/foo.git/info/refs
    effective: http://example.com/bar.git/info/refs

Subsequent requests will not be for "info/refs", but for
other paths relative to the base. We must ask the caller to
pass in the original base, and we must pass the redirected
base back to the caller (so that it can generate more URLs
from it). Furthermore, we need to feed the new base to the
credential code, so that requests to credential helpers (or
to the user) match the URL we will be requesting.

This patch teaches http_request_reauth to do this munging.
Since it is the caller who cares about making more URLs, it
seems at first glance that callers could simply check
effective_url themselves and handle it. However, since we
need to update the credential struct before the second
re-auth request, we have to do it inside http_request_reauth.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
remote-curl: make refs_url a strbuf

In the discover_refs function, we use a strbuf named
"buffer" for multiple purposes. First we build the info/refs
URL in it, and then detach that to a bare pointer. Then, we
use the same strbuf to store the result of fetching the
refs.

Let's instead keep a separate refs_url strbuf. This is less
confusing, as the "buffer" strbuf is now used for only one
thing.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
remote-curl: store url as a strbuf

We use a strbuf to generate the string containing the remote
URL, but then detach it to a bare pointer. This makes it
harder to later manipulate the URL, as we have forgotten the
length (and the allocation semantics are not as clear).

Let's instead keep the strbuf around. As a bonus, this
eliminates a confusing double-use of the "buf" strbuf in
main(). Prior to this, it was used both for constructing the
url, and for reading commands from stdin.

The downside is that we have to update each call site to
refer to "url.buf" rather than just "url" when they want the
C string.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
remote-curl: rewrite base url from info/refs redirects

For efficiency and security reasons, an earlier commit in
this series taught http_get_* to re-write the base url based
on redirections we saw while making a specific request.

This commit wires that option into the info/refs request,
meaning that a redirect from

    http://example.com/foo.git/info/refs

to

    https://example.com/bar.git/info/refs

will behave as if "https://example.com/bar.git" had been
provided to git in the first place.

The tests bear some explanation. We introduce two new
hierearchies into the httpd test config:

  1. Requests to /smart-redir-limited will work only for the
     initial info/refs request, but not any subsequent
     requests. As a result, we can confirm whether the
     client is re-rooting its requests after the initial
     contact, since otherwise it will fail (it will ask for
     "repo.git/git-upload-pack", which is not redirected).

  2. Requests to smart-redir-auth will redirect, and require
     auth after the redirection. Since we are using the
     redirected base for further requests, we also update
     the credential struct, in order not to mislead the user
     (or credential helpers) about which credential is
     needed. We can therefore check the GIT_ASKPASS prompts
     to make sure we are prompting for the new location.
     Because we have neither multiple servers nor https
     support in our test setup, we can only redirect between
     paths, meaning we need to turn on
     credential.useHttpPath to see the difference.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
C: have space around && and || operators

Correct all hits from

    git grep -e '\(&&\|||\)[^ ]' -e '[^	 ]\(&&\|||\)' -- '*.c'

i.e. && or || operators that are followed by anything but a SP,
or that follow something other than a SP or a HT, so that these
operators have a SP around it when necessary.

We usually refrain from making this kind of a tree-wide change in
order to avoid unnecessary conflicts with other "real work" patches,
but in this case, the end result does not have a potentially
cumbersome tree-wide impact, while this is a tree-wide cleanup.

Fixes to compat/regex/regcomp.c and xdiff/xemit.c are to replace a
HT immediately after && with a SP.

This is based on Felipe's patch to bultin/symbolic-ref.c; I did all
the finding out what other files in the whole tree need to be fixed
and did the fix and also the log message while reviewing that single
liner, so any screw-ups in this version are mine.

Signed-off-by: Felipe Contreras <felipe.contreras@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
alias: have SP around arithmetic operators

Signed-off-by: Felipe Contreras <felipe.contreras@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
abspath.c: have SP around arithmetic operators

Signed-off-by: Junio C Hamano <gitster@pobox.com>
alloc.c: have SP around arithmetic operators

Signed-off-by: Junio C Hamano <gitster@pobox.com>