Respect XDG_CACHE_HOME

The XDG Base Directory specification [1] demands that there should be a
"single base directory relative to which user-specific non-essential
(cached) data should be written". Light currently makes use of such a
cache directory, but hardcodes the default "$HOME/.cache".

In order to enable users to specify a custom cache directory, respect
this convention and use the "$XDG_CACHE_HOME" environment variable if it
is set. If it is not set, fall back to "$HOME/.cache".

[1] https://specifications.freedesktop.org/basedir-spec/basedir-spec-latest.html

Brillo merges

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>

ChangeLog updates, Debian packaging support

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>

We may need to drop the $prefix to the udev rules from configure.ac

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>

Doc updates

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>

Add --with-udev[=PATH] to configure script, for non-SUID root operation

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>

When light is installed in the non-SUID root mode it cannot write to
/etc/light anymore, so we set up a ~/.cache/light instead.

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>

This patch adds support for installing the 90-backlight.rules to gain
privileges to the kernel sysfs files.  By default the classic SUID root
mode is used and the rules file is not installed.

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>

Add Fedora installation instructions

Coding style

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>

Misc

- Use version from configure script
- Simplify usage text for accessibility, only one command at a time
- Simplify terminology, we have commands and options to commands

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>

Most users want to see the examples as early as possible, so we place
them directly after the new (simplified) introduction.  The examples
have been rewritten to separate commands from options and grouping
the command with its value, where applicable.

The rest of the document has just been auto-filled to fit to < 72
columns and sections now use === and ---- for headings to make the
README more accessible from a terminal.

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>

Unused file.

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>

Convert build system to GNU configure & build

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>

Add proper light.1 man page, removes help2man dependency

Better Support for Overriding Install Prefix

Address #27

This patch adds a standard configure script and converts the Makefile to
automake.  This adresses PR #30, but in a more generic way, and also
eliminates the hard coded CC variable, enabling building with clang or
even a cross compiler.

Note: this is more a proof of concept and does not include the man page
      generation.  Another pull request addresses that.

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>

Fix save and restore arguments

By not always appending "/usr" to the path, it enables install into /usr/local
and better integration with tools like stow.

Without this patch -O and -I are not supported anymore and lead to an
error.