scripts/update-version.sh modifies git-managed files

[aws]

scripts/update-version.sh modifies git-managed files

[samuelkarp]

I'm okay in general with modifying git-managed files, as long as the file that is checked in to git doesn't contain references that are invalid. In the ECS agent, we manage this by having the file set the git sha to UNKNOWN when checked in, but set to the real sha during builds.

The other way that people typically do things like this with Go + git is by setting the value of a variable at build time with a linker option (something like go build -ldflags "-X version.GitSha=${SHA}"). I'm not terribly opposed to this pattern either, but if we want to switch here I'd prefer that we switch in our other projects too (consistency is important).

[samuelkarp]

Fixed by #91.