I think I have the same problem. I've gotten my package to install with a fresh Packrat environment but after a short period of usage I get the same kind of Error in getrootdir(untar(src, list = TRUE)) : length(file_list) > 0 is not TRUE.

Here is my full error:

Downloading GitHub repo eturkes/eturkesRutils@master
/usr/bin/tar: This does not look like a tar archive

gzip: stdin: unexpected end of file
/usr/bin/tar: Child returned status 1
/usr/bin/tar: Error is not recoverable: exiting now
/usr/bin/tar: This does not look like a tar archive

gzip: stdin: unexpected end of file
/usr/bin/tar: Child returned status 1
/usr/bin/tar: Error is not recoverable: exiting now
Error in getrootdir(untar(src, list = TRUE)) : 
  length(file_list) > 0 is not TRUE
In addition: Warning messages:
1: In utils::untar(tarfile, ...) :
  ‘/usr/bin/tar -xf '/tmp/RtmpUh5cSC/file13a24b501c40.tar.gz' -C '/tmp/RtmpUh5cSC/remotes13a261c38292'’ returned error code 2
2: In system(cmd, intern = TRUE) :
  running command '/usr/bin/tar -tf '/tmp/RtmpUh5cSC/file13a24b501c40.tar.gz'' had status 2

And R.version:

platform       x86_64-suse-linux-gnu       
arch           x86_64                      
os             linux-gnu                   
system         x86_64, linux-gnu           
status                                     
major          3                           
minor          5.3                         
year           2019                        
month          03                          
day            11                          
svn rev        76217                       
language       R                           
version.string R version 3.5.3 (2019-03-11)
nickname       Great Truth   

EDIT:
Just want to add that I get the same error with "rstudio/packrat" and "cmap/cmapR" as a test. If I use a nonexistent repo name I get the standard HTTP error 404, so the problem isn't that R is unable to reach the Github repo. Same issues when using remotes.

A possibly related issue is tracked in remotes is #350 . No replies from a maintainer on that thread either, though.

What does Sys.getenv("TAR") return? The most likely explanation is it is pointing to something non-standard

I have similar issue as describd by @eturkes. Sys.getenv("tar") returns ""
Sys.getenv("TAR") returns "/bin/tar"

Interesting I get nearly the same results as @XiangZhangSC .

> Sys.getenv("tar")
[1] ""
> Sys.getenv("TAR")
[1] "/usr/bin/tar"

EDIT:
I get the same results regardless of whether I am in a Packrat project with a working install_github or not.

Sorry it should be capitalized, could you run

system2(Sys.getenv("TAR"), "--version")

tar (GNU tar) 1.30
Copyright (C) 2017 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>.
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

Written by John Gilmore and Jay Fenlason.

This is in a working Packrat installation. All my installations are "fresh" at the moment because my R version was just updated by my package manager. If I manage to create a "broken" installation, I'll let you know if how the tar version output matches up.

EDIT:
Got a broken install again! Get the same output as above when I run the command.

Bugfix
If:

getOption("download.file.method")
[1] "curl"

Then:
options("download.file.method" = "libcurl")

(edited to correct getOption() spelling )

Can confirm that @franzbischoff's solution works on a previously broken installation. Thank you so much!

One small correction though, getOptions should be getOption.

Thank you so much for this because this had been frustrating me to no end.

Linux user here (Linux Mint 19). For what it's worth, I tried writing this to my .Rprofile and it kept breaking Rstudio whenever I'd try to install or update any package (from CRAN or Github). I could install from the terminal/console just fine, however.

I wish I knew why this was the case but it might be a fix you do a la carte whenever you want to install an R package from Github in a given session.