Import default username from 'git config github.user'

[tyru]

Import default GitHub username from git config github.user if it is present.
This PR can get rid of duplicate configuration in .vimrc and .gitconfig .

[tyru]

FYI, themis command fails on my local machine...
I don't know this is a problem, just to tell you.

$ themis
Bail out!  Error occurred in script loading.
# function vital#of(name) abort  Line:4  (~/.vim/bundle/vim-themis/autoload/vital.vim)
#   4:     throw 'vital: version file not found: ' . a:name
# vital: version file not found: vital

[lambdalisue]

FYI, themis command fails on my local machine...
I don't know this is a problem, just to tell you.

You need to create ~/.themisrc like

call themis#option('runtimepath', expand('~/.vim/bundle/vimproc.vim'))
call themis#option('runtimepath', expand('~/.vim/bundle/vital.vim'))

Or apply --runtimepath options to themis command ;-)

[lambdalisue]

Please define s:R = s:V.import('Process') at the top of this file and use s:R.system() instead.

Additionally, please add a switch variable (say, g:gista#client#use_git_config_github_user) at the bottom of this file (the default value should be 0) and use it to check if gista should call git config github.user.
It is required because

1. Calling system would slow the response
2. Some users may want to use vim-gista as an anonymous mode in default. This part is called when a new client is created, mean that it will be called by any :Gista XXX command so without switch option. That's why users require to call :Gista logout everytime after vim started if they want to use vim-gista as an anonymous mode in default.

And please add documentation about the variable around

https://github.com/lambdalisue/vim-gista/blob/master/doc/vim-gista.txt#L124
https://github.com/lambdalisue/vim-gista/blob/master/doc/vim-gista.txt#L256
https://github.com/lambdalisue/vim-gista/blob/master/doc/vim-gista.txt#L471

[lambdalisue]

Thanks for implementation. I pointed two things so please fix these ;-)

[tyru]

Okay.
I will fix those for later.

[lambdalisue]

I changed my mind. The default value of the option should be 1 while majority of people prefer to login I guess.

[tyru]

Okay :)

[tyru]

Fixed.
Please confirm it.

[lambdalisue]

LGTM. Could you add document?

[tyru]

Added.

[lambdalisue]

Thanks a lot ;~) I'll add other documents later.

[tyru]

My pleasure!