Fix backslash issue when using tmpdir as regexp on Windows in install_theme

[gadenbuie]

As reported at https://stackoverflow.com/questions/49212335/r-blogdown-new-site-throws-error, the use of the tempfile() result as a regexp in install_theme() causes problems on Windows.

What I found was that tmpdir = tempfile("", ".") returns a string like ".\\dir", whereas the filenames returned by utils::unzip(..., exdir = tmpdir) are "./dir/zip_base_dir.

For example:

Browse[2]> tmpdir
[1] ".\\2a0c6c64f7e"
Browse[2]> zipdir
[1] "./2a0c6c64f7e/hugo-lithium-theme-master"

This PR replaces the double backslash with a single forward slash when stripping the tmpdir prefix from zipdir and seems to work on Windows and Unix-alike (where there are no backslashes to match).

Session info for Windows test

> sessioninfo::session_info()
─ Session info ──────────────────────────────────────────────────────────────────────────────
 setting  value                       
 version  R version 3.4.0 (2017-04-21)
 os       Windows 7 x64 SP 1          
 system   x86_64, mingw32             
 ui       RStudio                     
 language (EN)                        
 collate  English_United States.1252  
 tz       America/New_York            
 date     2018-03-11                  

─ Packages ──────────────────────────────────────────────────────────────────────────────────
 package     * version date       source        
 backports     1.0.5   2017-01-18 CRAN (R 3.4.0)
 blogdown    * 0.5.9   <NA>       local         
 bookdown      0.7     2018-02-18 CRAN (R 3.4.3)
 clisymbols    1.2.0   2017-05-21 CRAN (R 3.4.3)
 commonmark    1.4     2017-09-01 CRAN (R 3.4.3)
 devtools      1.13.5  2018-02-18 CRAN (R 3.4.3)
 digest        0.6.15  2018-01-28 CRAN (R 3.4.3)
 evaluate      0.10    2016-10-11 CRAN (R 3.4.0)
 htmltools     0.3.6   2017-04-28 CRAN (R 3.4.3)
 httpuv        1.3.6.2 2018-03-02 CRAN (R 3.4.3)
 knitr         1.20    2018-02-20 CRAN (R 3.4.3)
 later         0.7.1   2018-03-07 CRAN (R 3.4.3)
 magrittr      1.5     2014-11-22 CRAN (R 3.4.0)
 memoise       1.1.0   2017-04-21 CRAN (R 3.4.0)
 mime          0.5     2016-07-07 CRAN (R 3.4.0)
 R6            2.2.2   2017-06-17 CRAN (R 3.4.3)
 Rcpp          0.12.10 2017-03-19 CRAN (R 3.4.0)
 RcppTOML      0.1.3   2017-04-25 CRAN (R 3.4.3)
 rlang         0.2.0   2018-02-20 CRAN (R 3.4.3)
 rmarkdown     1.9     2018-03-01 CRAN (R 3.4.3)
 roxygen2      6.0.1   2017-02-06 CRAN (R 3.4.3)
 rprojroot     1.2     2017-01-16 CRAN (R 3.4.0)
 rstudioapi    0.7     2017-09-07 CRAN (R 3.4.3)
 servr         0.8     2017-11-06 CRAN (R 3.4.3)
 sessioninfo   1.0.0   2017-06-21 CRAN (R 3.4.3)
 stringi       1.1.6   2017-11-17 CRAN (R 3.4.2)
 stringr       1.3.0   2018-02-19 CRAN (R 3.4.3)
 withr         2.1.1   2017-12-19 CRAN (R 3.4.3)
 xfun          0.1     2018-01-22 CRAN (R 3.4.3)
 xml2          1.2.0   2018-01-24 CRAN (R 3.4.3)
 yaml          2.1.18  2018-03-08 CRAN (R 3.4.3)

[yihui]

Hmm. It is a little odd that unzip() always returns paths that use / as the path separator.

[yihui]

Thanks! Could you also post an answer to the SO question?

BTW, in this particular case, it is absolutely appropriate for the user to report to the Github repo here (because it is a bug). In general, I hope they could try StackOverflow first:

• https://github.com/rstudio/blogdown/issues/new
• https://yihui.name/en/2017/08/so-gh-email/

because average users probably don't really know if an issue is a bug or misuse. I'd rather bugs being reported on StackOverflow (I have subscribed to the relevant tags by RSS) than questions being asked in a Github repo, because I cannot handle the latter.

[gadenbuie]

Sure, just posted an answer. I completely understand SO vs. GH, I've been watching a couple repos and definitely see the logic to that ordering ;)

Thank you for the code review and notes in 2823c95, those changes make a lot of sense. Hope you're feeling better!