Include git SHA or R package version in metadata for all returned data frames

[seananderson]

Append the R package version or Git SHA into the metadata of the output from the main cache data function... and maybe even all the data frames. (attributes, list element, or data frame column)

[cgrandin]

We can use system() to call git and get the current SHA: https://stackoverflow.com/questions/46376966/how-to-get-sha-of-current-git-commit-from-r

Is the idea to attach this to every saved object, i.e. add a list element called "meta" or something and have is as a sub-list containing the SHA and R package versions or is there a metadata structure in place already?

[seananderson]

I don't think I'd want to rely on system and git because not all users will have Git and not all will have it in their path... oh, more importantly people don't usually use the functions from within the package folder.

My guess is we'd be best off grabbing the installed package version number (and have to be religious about always bumping that). Maintaining an internal object that has the last SHA would be messy since updating it would add a commit.

My guess is attributes is the best place to store this.

[cgrandin]

That makes a lot of sense - What about using git hooks to run a script on each commit which updates a file in inst/ext containing the SHA of the commit? Then there's nothing to remember to do each time and I know I will forget.

There is an example of one for pre-commit in .git/hooks/pre-commit.sample