Select lexer with --filename argument

[douglas-larocca]

cgit's syntax highlighting filter pipes to STDIN and provides the
filename in argv; the analyzer often fails but we have access to the
original filename, so we add an optional argument to specify the
filename to use for matching a lexer when reading from STDIN; when
[files...] are provided to chroma this is completely ignored

[douglas-larocca]

For reference, the cgit source filter script being used to wrap chroma:

#!/bin/sh
exec chroma --unbuffered --filename=$1 --style=pastie --html --html-inline-styles --html-only

From the cgit docs:

source filter::
	This filter is given a single parameter: the filename of the source
	file to filter. The filter can use the filename to determine (for
	example) the syntax highlighting mode. The contents of the source
	file that is to be filtered is available on standard input and the
	filtered contents is expected on standard output.

[alecthomas]

Seems like a good idea, thanks.