change the branch name to docs,get `'deploy:gh' errored

[fanqi]

i found setting way to change github branch, edit electric.config.js,add deployOptions: { branch: 'gh-pages' }, it successed，but i change the branch name to docs，i get 'deploy:gh' errored after 691 ms

[13:01:29] 'deploy:gh' errored after 691 ms
[13:01:29] Error in plugin 'gulp-gh-pages'
Message:
    Command failed: git rev-list --pretty=raw --skip=0 --max-count=10 docs
fatal: ambiguous argument 'docs': both revision and filename
Use '--' to separate paths from revisions, like this:
'git <command> [<revision>...] -- [<file>...]'

Details:
    killed: false
    code: 128
    signal: null
    cmd: git rev-list --pretty=raw --skip=0 --max-count=10 docs
Finished 'deploy'...