Return absolute paths unchanged

[krlmlr]

If the first component is already an absolute path, everything is returned unchanged. This applies to find_root_file() and the criteria's "member functions".

Fixes r-lib/here#34, fixes r-lib/here#31.

Closes #46.

@jthurner @StevenMMortimer @czeildi @lgaborini: Would that make {here} easier to use?

@yihui: What do you think about this approach for handling paths that are already absolute, in {here} and {rprojroot}?

[StevenMMortimer]

@krlmlr Makes sense and seems to be a great solution to dealing with a combination of absolute and relative paths. Thanks for working on it!

[jthurner]

@krlmlr
Yes, much better fix for r-lib/here#34 and r-lib/here#31 than my PR. Thanks!

[codecov-io]

Codecov Report

Merging #59 (b9e5eac) into master (4999f9a) will decrease coverage by 1.25%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master      #59      +/-   ##
==========================================
- Coverage   81.25%   80.00%   -1.25%     
==========================================
  Files           5        6       +1     
  Lines         192      185       -7     
==========================================
- Hits          156      148       -8     
- Misses         36       37       +1     

Impacted Files	Coverage Δ
R/absolute.R	100.00% <100.00%> (ø)
R/criterion.R	81.13% <100.00%> (-8.00%)	⬇️
R/file.R	100.00% <100.00%> (ø)
R/thisfile.R	51.21% <0.00%> (-9.44%)	⬇️
R/has-file.R	98.27% <0.00%> (+0.09%)	⬆️

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[czeildi]

Looks great, thanks a lot for your work, this will definitely improve my workflow.

[krlmlr]

Thanks for your feedback!

[lgaborini]

Looking good! Thanks!

[yihui]

@krlmlr That makes sense to me. Thanks!