cache: don't leave cache_slot fields uninitialized

Valgrind says:

==18344== Conditional jump or move depends on uninitialised value(s)
==18344==    at 0x406C83: open_slot (cache.c:63)
==18344==    by 0x407478: cache_ls (cache.c:403)
==18344==    by 0x404C9A: process_request (cgit.c:639)
==18344==    by 0x406BD2: fill_slot (cache.c:190)
==18344==    by 0x4071A0: cache_process (cache.c:284)
==18344==    by 0x404461: main (cgit.c:952)
==18344==  Uninitialised value was created by a stack allocation
==18344==    at 0x40738B: cache_ls (cache.c:375)

This is caused by the keylen field being used to calculate whether or
not a slot is matched.  We never then check the value of this and the
length of data read depends on the key length read from the file so this
isn't dangerous, but it's nice to avoid branching based on uninitialized
data.

Signed-off-by: John Keeping <john@keeping.me.uk>
tests: add Valgrind support

Now running tests with the "--valgrind" option will run cgit under
Valgrind instead of all Git commands.

Signed-off-by: John Keeping <john@keeping.me.uk>
html: remove redundant htmlfd variable

This is never changed from STDOUT_FILENO, so just use that value
directly.

Signed-off-by: John Keeping <john@keeping.me.uk>
ui-snapshot: set unused cgit_filter fields to zero

By switching the assignment of fields in the cgit_filter structure to
use designated initializers, the compiler will initialize all other
fields to their default value.  This will be needed when we add the
extra_args field in the next patch.

Signed-off-by: John Keeping <john@keeping.me.uk>
filter: pass extra arguments via cgit_open_filter

This avoids poking into the filter data structure at various points in
the code.  We rely on the fact that the number of arguments is fixed
based on the filter type (set in cgit_new_filter) and that the call
sites all know which filter type they're using.

Signed-off-by: John Keeping <john@keeping.me.uk>
ui-refs: escape HTML chars in author and tagger names

Everywhere else we use html_txt to escape any special characters in
these variables.  Do so here as well.

Signed-off-by: John Keeping <john@keeping.me.uk>
ui-shared: URL-escape script_name

As far as I know, there is no requirement that $SCRIPT_NAME contain only
URL-safe characters, so we need to make sure that any special characters
are escaped.

Signed-off-by: John Keeping <john@keeping.me.uk>
ui-repolist: HTML-escape cgit_rooturl() response

This is for consistency with other callers.  The value returned from
cgit_rooturl is not guaranteed to be HTML-safe.

Signed-off-by: John Keeping <john@keeping.me.uk>
tests: add CGIT_TEST_OPTS variable to Makefile

This allows running the entire test suite with a set of command-line
options.  For example:

	make test CGIT_TEST_OPTS=--valgrind

Signed-off-by: John Keeping <john@keeping.me.uk>
filters: Improved syntax-highlighting.py

- Switched back to python2 according to a problem in pygments with python3.
  With the next release of pygments this problem should be fixed.
  Issue see here:
  https://bitbucket.org/birkenfeld/pygments-main/issue/901/problems-with-python3
- Just read the stdin, decode it to utf-8 and ignore unknown signs. This ensures
  that even destroyed files do not cause any errors in the filter.
- Improved language guessing:
  -> At first use guess_lexer_for_filename for a better detection of the used
     programming languages (even mixed cases will be detected, e.g. php + html).
  -> If nothing was found look if there is a shebang and use guess_lexer.
  -> As default/fallback choose TextLexer.

Signed-off-by: Stefan Tatschner <stefan@sevenbyte.org>
authors: specify maintainers

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
filter: add fprintf_filter function

This stops the code in cgit.c::print_repo needing to inspect the
cgit_filter structure, meaning that we can abstract out different filter
types that will have different fields that need to be printed.

Signed-off-by: John Keeping <john@keeping.me.uk>
filter: add interface layer

Change the existing cgit_{open,close,fprintf}_filter functions to
delegate to filter-specific implementations accessed via function
pointers on the cgit_filter object.

We treat the "exec" filter type slightly specially here by putting its
structure definition in the header file and providing an "init" function
to set up the function pointers.  This is required so that the
ui-snapshot.c code that applies a compression filter can continue to use
the filter interface to do so.

Signed-off-by: John Keeping <john@keeping.me.uk>
filter: introduce "filter type" prefix

This allows different filter implementations to be specified in the
configuration file.  Currently only "exec" is supported, but it may now
be specified either with or without the "exec:" prefix.

Signed-off-by: John Keeping <john@keeping.me.uk>
filter: allow for cleanup hook for filter types

At some point, we're going to want to do lazy deallocation of filters.
For example, if we implement lua, we'll want to load the lua runtime
once for each filter, even if that filter is called many times.
Similarly, for persistent exec filters, we'll want to load it once,
despite many open_filter and close_filter calls, and only reap the child
process at the end of the cgit process. For this reason, we add here a
cleanup function that is called at the end of cgit's main().

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
filter: basic write hooking infrastructure

Filters can now call hook_write and unhook_write if they want to
redirect writing to stdout to a different function. This saves us from
potential file descriptor pipes and other less efficient mechanisms.

We do this instead of replacing the call in html_raw because some places
stdlib's printf functions are used (ui-patch or within git itself),
which has its own internal buffering, which makes it difficult to
interlace our function calls. So, we dlsym libc's write and then
override it in the link stage.

While we're at it, we move considerations of argument count into the
generic new filter handler.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
filter: add lua support

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
filter: return on null filter from open and close

So that we don't have to include the if(filter) open_filter(filter)
block everywhere, we introduce the guard in the function itself. This
should simplify quite a bit of code.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
filter: add support for email filter

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
filter: add gravatar scripts

The lua one is hugely faster than the python one, but both are included
for comparison.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>