Specifically, make it match the signs' foreground colours; and clear the
backgrounds so the GitGutter{Add,Delete}IntraLine highlights' "reverse"
colours work properly.
Previously if the user or the colourscheme had already defined
GitGutter* highlight groups, the plugin would leave their backgrounds
alone. This pushed the responsibility for figuring out and specifying
the correct backgrounds onto the user or colourscheme maintainer.
With this change the plugin now sets the correct background on existing
GitGutter* highlight groups.
Also, the documentation was simplified so it is clearer how to set your
own colours for the signs.
Originally the plugin used fresh temp files for every diff. But it
wrote to those files with `:write` which made Vim's buffer numbers
increase unnecessarily (see #297) so the plugin changed to reuse the
same temp files each time (see a871d857).
However this has the problem that after Vim has been open for a while,
e.g. a few days, the operating system can clean up the temp directory
holding those temp files. The next time the plugin runs a diff, Vim
throws an error because it cannot write to the temp files because their
directory has disappeared (see #395, #433).
In the meantime the plugin changed how it writes the temp files to
use `writefile()` (see 4e911819). This removed the problem of rapidly
increasing buffer numbers.
Now the buffer number problem has gone, the plugin can revert to using
fresh temp files each time.
win_getid() was introduced in Vim 7.4.1557. The code uses it to
remember the id of the preview window. In newer Vims or Neovim this
could be a floating window but pre-7.4.1557 it can only be an ordinary
preview window. And in that case we only need the preview window's
buffer number.
This commit uses the buffer number when win_getid() isn't available.
Fixes#683.
When you look at previous versions of a file, e.g. with Fugitive's
:0Gclog, gitgutter will set the diff base to the current version's
parent so that diff markers appear as expected.
Thannks to @rcreasi for the idea and initial implementation.
