ui-shared: fix return type of cgit_self_link

cgit_self_link() is a void function but implements each case it handles
by doing "return <another_void_function>" which is not valid C; section
6.8.6.4 of C11 says:

	A return statement with an expression shall not appear in a
	function whose return type is void.

Fix this by removing the return keywords and converting the final code
block into an "else".

Signed-off-by: John Keeping <john@keeping.me.uk>
Merge branch 'wip'
Makefile: re-use Git's Makefile where possible

Git does quite a lot of platform-specific detection in its Makefile,
which can result in it defining preprocessor variables that are used in
its header files.  If CGit does not define the same variables it can
result in different sizes of some structures in different places in the
same application.

For example, on Solaris Git uses it's "compat" regex library which has a
different sized regex_t structure than that available in the platform
regex.h.  This has a knock-on effect on the size of "struct rev_info"
and leads to hard to diagnose runtime issues.

In order to avoid all of this, introduce a "cgit.mk" file that includes
Git's Makefile and make all of the existing logic apply to CGit's
objects as well.  This is slightly complicated because Git's Makefile
must run in Git's directory, so all references to CGit files need to be
prefixed with "../".

In addition, OBJECTS is a simply expanded variable in Git's Makefile so
we cannot just add our objects to it.  Instead we must copy the two
applicable rules into "cgit.mk".  This has the advantage that we can
split CGit-specific CFLAGS from Git's CFLAGS and hence avoid rebuilding
all of Git whenever a CGit-specific value changes.

Signed-off-by: John Keeping <john@keeping.me.uk>
Acked-by: Jamie Couture <jamie.couture@gmail.com>
ui-patch: use cgit_version not CGIT_VERSION

We already have a global cgit_version which is set from the #define'd
CGIT_VERSION in cgit.c.  Change ui-patch.c to use this so that we only
need to rebuild cgit.o when the version changes.

Signed-off-by: John Keeping <john@keeping.me.uk>
cgit.mk: don't rebuild everything if CGIT_VERSION changes

If CGIT_VERSION is in CGIT_CFLAGS then a change in version (for example
because you have committed your changes) causes all of the CGit objects
to be rebuilt.  Avoid this by using EXTRA_CPPFLAGS to add the version
for only those files that are affected and make them depend on VERSION.

Signed-off-by: John Keeping <john@keeping.me.uk>
cgit.mk: Use SHELL_PATH_SQ to run gen-version.sh

On some platforms (notably Solaris) /bin/sh doesn't support enough of
POSIX for gen-version.sh to run.  Git's Makefile provides SHELL_PATH_SQ
to address this issue so we just have to use it.

Signed-off-by: John Keeping <john@keeping.me.uk>
ui-shared: squelch compiler warning.

Since tail is initialized to 0, we will never get a warning on the last
if statement, but recent gcc complains anyway. So, we initialize len as
well. Future gcc versions should be able to optimize this out anyway.
html: check return value of write

This squelches a gcc warning. It's also correct that we check to see if
there are any partial or failed writes. For now, we just print a warning
to stderr. In the future, perhaps it will prove wise to exit(1) on
partial writes.
Fix colspan values

This fixes a couple of minor oversights in previous commits and adjusts
all cells using colspan to use the correct width.

Signed-off-by: Lukas Fleischer <cgit@cryptocrack.de>
ui-summary.c: Move urls variable into print_urls()

There's no need for this variable to be global. Printing the header in
print_urls() instead of print_url() allows for moving this variable into
print_urls() without having to pass any status to print_url().

Note that this only works as long as we don't call print_urls() more
than once.

Signed-off-by: Lukas Fleischer <cgit@cryptocrack.de>