Add exit codes that indicate what went wrong

[olsen232]

Useful for any app built on top of sno - until now, any error caused an exit code of either 1 or 2 (except in sno diff --exit-code where all errors caused exit code 2).

See exceptions.py for a list of exit codes so far. More can be added later as needed.

SUCCESS = 0
SUCCESS_WITH_FLAG = 1
(which basically means, you sno ran diff --exit-code and there was a diff)

INVALID_ARGUMENT = 2

UNCATEGORIZED_ERROR = 10

INVALID_OPERATION = 20

NOT_YET_IMPLEMENTED = 30

NOT_FOUND = 40
NO_REPOSITORY = 41
NO_DATA = 42
NO_BRANCH = 43
NO_CHANGES = 44
NO_WORKING_COPY = 45
NO_USER = 46
NO_COMMIT = 47
NO_IMPORT_SOURCE = 48
NO_TABLE = 49

SUBPROCESS_ERROR = 128+x
(x is the error from the subprocess)

[rcoup]

1. I think sno diff --exit-code should match git diff --exit-code behaviour.

Others are all pretty minor suggestions, I don't feel strongly about them:

2. 2 is pretty standard for bad-syntax/arguments/options IME?
3. why not make UNCATEGORIZED_ERROR = 1?
4. subprocess-launch-error 128 ?
5. subprocess error: `128+(subprocess exit code)?

[olsen232]

1. I think sno diff --exit-code should match git diff --exit-code behaviour.
   Yup this is done. 0 is same, 1 is diff.

2. 2 is pretty standard for bad-syntax/arguments/options IME?
   Made INVALID_ARGUMENT 2

3. why not make UNCATEGORIZED_ERROR = 1?
   This would work except in --exit-code mode, in which case, it would need a different value.
   Seems easiest just to make it the same number all the time.
   Made it 11 which is a very one-ish number.

4. subprocess-launch-error 128 ?
   subprocess error: `128+(subprocess exit code)?
   Done

[craigds]

👍