All VCS assume slightly different things where things have to be if you're in
this directory using that command etc.
Changing to the directory of the current file avoids many pitfalls.
When you have nested repos of different VCS and you edit a file from the inner
repo, more than one VCS can return a valid diff. Only one VCS should return a
non-empty diff, though.
Once a non-empty diff is found, all other VCS get disabled to reduce overhead.
References #235.
Before this change, it was possible that a buffer was disabled, when Sy was run
more than once at startup, e.g. because of `BufEnter` and `FocusGained`.
The first call would start the detection and the second call would disable the
buffer, because the first call hadn't changed the VCS type from "unknown" yet.
To avoid issues for Vim versions between 7.4.1966 and 7.4.2071, we now use
type() to distinguish between the type of variable `job_id` being either Number
or Job.
Before Vim 8.0.50, an exited job was only detected with a potentially huge
delay.
Thus, for versions smaller than 8.0.50, we add a close_cb callback that runs
job_status() which in return runs the exit_cb callback immeditely if the job was
found to be dead.
Vim patch:
01688ad545
References: #216.
Since we don't switch the window anymore, we can't simply refer to b:sy as we
used to do while Sy worked only synchronously.
Now we provide the buffer number to each job and the exit handler gets a pointer
to the b:sy of that buffer and passes it to all the subsequent functions.
References #209, #210.
Vim provides 2 arguments to the exit handler whereas Neovim always provides 3.
Change function signature to handle an optional third argument, even if it never
gets used.
Fixes#204.
