Improvements to tag, commit, and signature parsing

odb_pack: don't do ambiguity checks for fully qualified SHA1 hashes

This makes libgit2 more closely match Git, which only checks for
ambiguous pack entries when given short hashes.

Note that the only time this is ever relevant is when a pack has the
same object more than once (it's happened in the wild, I promise).

When trying to find the end of an email, instead of starting at the
beginning of the signature, we start at the end of the name (after the
first '<').

This brings libgit2 more in line with Git's behavior when reading out
existing signatures.

However, note that Git does not allow names like these through the
usual porcelain; instead, it silently strips any '>' characters it
sees.

Instead of bailing out with an error, this sets tagger to NULL when
the field is missing from the object.

This makes it possible to inspect tags like this one:

http://git.kernel.org/?p=git/git.git;a=tag;h=f25a265a342aed6041ab0cc484224d9ca54b6f41

The v0.99 tag in the Git repo triggers this behavior:

http://git.kernel.org/?p=git/git.git;a=tag;h=d6602ec5194c87b0fc87103ca4d67251c76f233a

Ideally, we'd allow the tag to be instantiated even though the tagger
field is missing, but this at the very least prevents libgit2 from
crashing.

To test this bug, a new repository has been added based on the test
branch in testrepo.git. It contains a "e90810b" tag that looks like
this:

    object e90810b8df3e80c413d903f631643c716887138d
    type commit
    tag e90810b

    This is a very simple tag.

This ensures commit->message is always non-NULL, even if the commit
message is empty or consists of only a newline.

One such commit can be found in the wild in the jQuery repository:

https://github.com/jquery/jquery/commit/25b424134f9927a5bf0bab5cba836a0aa6c3cfc1

Put them all together so we know where to find them.

Signed-off-by: Carlos Martín Nieto <carlos@cmartin.tk>

Signed-off-by: Carlos Martín Nieto <carlos@cmartin.tk>

Unfortunately, we can't use the function in fetch.c due to chunked
encoding and keep-alive connections.

Signed-off-by: Carlos Martín Nieto <carlos@cmartin.tk>

Signed-off-by: Carlos Martín Nieto <carlos@cmartin.tk>

Using a different buffer in each function means that some data might
get lost. Store all the data in a buffer in the transport object.

Take this opportunity to use the generic download-pack function.

Signed-off-by: Carlos Martín Nieto <carlos@cmartin.tk>

Taken mostly from the git transport's version, this can be used by any
transport that takes its pack data from the network.

Signed-off-by: Carlos Martín Nieto <carlos@cmartin.tk>

It was a bad idea.

Signed-off-by: Carlos Martín Nieto <carlos@cmartin.tk>

Signed-off-by: Carlos Martín Nieto <carlos@cmartin.tk>

Signed-off-by: Carlos Martín Nieto <carlos@cmartin.tk>

Signed-off-by: Carlos Martín Nieto <carlos@cmartin.tk>

Signed-off-by: Carlos Martín Nieto <carlos@cmartin.tk>

Signed-off-by: Carlos Martín Nieto <carlos@cmartin.tk>

It's a bit awkward to run it as an extra step, and HTTP may need to
send the wants list several times.

Signed-off-by: Carlos Martín Nieto <carlos@cmartin.tk>

As we don't know the length of the message we want to send to the
other end, we send a chunk size before each message. In later
versions, sending the wants might benefit from batching the lines
together.

Signed-off-by: Carlos Martín Nieto <carlos@cmartin.tk>

Not every request needs a new connection if we're using a keep-alive
connection. Store the HTTP parser, host and port in the transport in
order to have it available in later calls.

Signed-off-by: Carlos Martín Nieto <carlos@cmartin.tk>

Include windows version information in git2.dll

Assorted CMake fixes

Signed-off-by: Carlos Martín Nieto <carlos@cmartin.tk>

If either CFLAGS is defined or the user passes -DCMAKE_C_FLAGS to
cmake, the variable already contains flags. Don't overwrite them, but
append them to our settings.

Signed-off-by: Carlos Martín Nieto <carlos@cmartin.tk>

This option is only ever used with MSVC.

Signed-off-by: Carlos Martín Nieto <carlos@cmartin.tk>

Signed-off-by: Carlos Martín Nieto <carlos@cmartin.tk>

A couple of fetch fixes

Signed-off-by: Sven Strickroth <email@cs-ware.de>

Signed-off-by: Sven Strickroth <email@cs-ware.de>

Signed-off-by: Sven Strickroth <email@cs-ware.de>

fix build for x64

Signed-off-by: Sven Strickroth <email@cs-ware.de>

We should always save the remote's HEAD as FETCH_HEAD locally.

Signed-off-by: Carlos Martín Nieto <carlos@cmartin.tk>

It's rare for a configured remote, but for one given as an URL on the
command line, it's more often than not the case.

Signed-off-by: Carlos Martín Nieto <carlos@cmartin.tk>