Add "-dirty" postfix to version string for uncommitted changes

[DEVoytas]

This is inspired by Linux kernel: https://github.com/torvalds/linux/blob/b244131/scripts/setlocalversion#L76

It may be useful for multiple reasons, for example:

• if someone raises a bug, and his version has -dirty postfix, then the person should be asked to reproduce it on unmodified version, in order to make sure the bug is not due to local changes.

This is how it works:

$ git status
On branch mark-uncommitted-changes-in-version
Your branch is up to date with 'origin/mark-uncommitted-changes-in-version'.

nothing to commit, working tree clean
$ subuser version | head -1
Subuser version: 0.6.2-dev-825feeb812e3f75dccb6ecc339f8c68541269fe6

$ echo "" >> logic/subuserlib/version.py
$ git status
On branch mark-uncommitted-changes-in-version
Your branch is up to date with 'origin/mark-uncommitted-changes-in-version'.

Changes not staged for commit:
  (use "git add <file>..." to update what will be committed)
  (use "git checkout -- <file>..." to discard changes in working directory)

        modified:   logic/subuserlib/version.py

no changes added to commit (use "git add" and/or "git commit -a")
$ subuser version | head -1
Subuser version: 0.6.2-dev-825feeb812e3f75dccb6ecc339f8c68541269fe6-dirty
$ git checkout logic/subuserlib/version.py
$ subuser version | head -1
Subuser version: 0.6.2-dev-825feeb812e3f75dccb6ecc339f8c68541269fe6

[timthelion]

I'm a bit disturbed by the fact that the version command still works after you run:

echo "" >> logic/subuserlib/version.py

[DEVoytas]

@timthelion why so? This is just adding empty line at the end of the file, so should not break anything ever. Just a random change to demonstrate version string changes :) Could well be any other change in any other tracked file. You can verify by yourself that echo "" >> logic/subuserlib/version.py does not prevent version command from working by checking out master, running above echo command and then issuing subuser version command.

[timthelion]

Aha, I made a reading comprehension error and read that as being echo "" > logic/subuserlib/version.py. My bad.