Merge `maint x.y` to `master`

$ reana-dev git-upgrade -c ALL
$ reana-dev git-checkout -c ALL master
$ cd reana-ui
$ reana-dev git-upgrade -c . --base maint-0.7
$ reana-dev git-upgrade -c .
$ git checkout -b merge
$ git log master..maint-0.7  # what changes we would merge?
$ git merge --log maint-0.7  
$ git status # file1.py and file2.py have conflicts
$ vim file1.py # solve conflicts
$ git add file1.py
$ vim file2.py # solve more conflicts
$ git add file2.py
$ git status # all clean
$ git merge --continue # we are done!
$ git diff master merge # inspect all code changes
$ reana-dev run-ci ... # try to run; whoops, it's broken
$ vim file3.py # some other file may needs adaptation
$ git add file3.py
$ git commit --amend
$ git show master:file4.py > file4.py # some yet another file may be easier to edit out again from its master state
$ vim file4.py
$ git add file4.py
$ git commit --amend
$ git diff master merge # one last look
$ reana-dev run-ci ... # let's retest

---

$ git push origin merge
$ gh pr create -t "Merge branch 'maint-0.7'" -b "addresses reanahub/reana#<ISSUE_NUMBER>" --web