Our logic for converting npm style versions to PEP-440 style versions
was not correct in some cases. This change fixes this.
As part of this change we no longer produce a NPM version that would
be just X.Y.Z-dev, instead for development versions we always include
both the timestamp of the commit and the commit hash.
Instead of trying to use a bunch of sed logic to do our conversions,
we now have a small go program that uses a newly added library in
pkg/util. A side effect of this is that we can more easily write tests
to ensure the conversion works as expected.
Fixes#1243
Our previous strategy of just using `git describe --tags --dirty` to
compute a version caused issues. The major one was that since version
sort lexigrapically, git's strategy of having a commit count without
leading zeros lead to cases where 0.11.0-dev-9 was "newer than"
0.11.0-dev-10 which is not what you want at all.
With this change, we compute a version by first seeing if the commit
is tagged, and if so, we use that tag. Otherwise, we take the closest
tag and to it append the unix timestamp of the commit and then append
a git hash.
Because we use the commit timestamp, things will sort correctly again.
Part of pulumi/home#174
