Fix revdep_check() when git2r is not loaded

[krlmlr]

When installing package during revdep check, use new libpath in addition to existing libpath. Reason: if git2r is not loaded yet, an error is raised if it not in the temporary library.

[jimhester]

This LGTM. I ran into this as well. I think this is a regression caused by the switch to withr. withr::with_libpaths has a default action of 'replace', while I believe the devtools version prepended.

[krlmlr]

There are two more instances of with_libpaths():

R/check-cran.r:51:  libpaths_orig <- withr::with_libpaths(libpath, {
R/build.r:72:  withr::with_libpaths(c(temp_lib, .libPaths()), R(cmd, path, quiet = quiet))

[jimhester]

I was wrong about it being a regression of set_libpaths, it did replace completely previously.

That first instance was deliberately changed to from prepending to replace at
516e59f. The second looks like we can replace with action = 'prefix'.

[krlmlr]

Merged with master, and replaced instance of with_libpaths() by with_temp_libpaths().

[hadley]

I think this maybe needs dependencies = TRUE

[krlmlr]

Restored lines killed when resolving merge conflicts, added "dependencies = TRUE".

[hadley]

BTW I think if you always add the NEWs bullet at the top, it's less likely to cause merge conflicts because it gets anchored to the unchanging heading. (That's my theory anyway)

[krlmlr]

Nope: I have put together a test script that simulates adding a bullet point to the top of the NEWS file, a merge conflict is raised when trying to merge the second branch. Using .gitattributes helps, but only locally, not on GitHub.

In my code, I record the NEWS entries in the bodies of the merge commit messages. Then, just before release, I use

git log --first-parent <tag>.. --format=format:"%b" | sed "/^$/d"

where <tag> is the last released tag. The log command lists precisely the merge commits, the sed removes empty lines.

[jimhester]

setting NEWS.md merge=union in the projects .gitattributes works locally, but GitHub ignores that setting when doing its merge. That is unfortunate 😦. It is probably still worth setting it for devtools as it would make local merging easier. isaacs/github#487 is the un-official issue for GitHub support for union merges.