Vectorization of the install_github function from devtools package in R - r

Question

I am using devtools package to install R packages from GitHub. In the function's manual there is a sentence about repo parameter that the function is vectorized on that parameter
This function is vectorised on repo so you can install multiple packages in a single command.
I've created 5 packages and I distribute them on a single github repository in 5 different subdirectories. When I use such command to install all 5 of them in a single function call
> if (!require(devtools)) {
+ install.packages("devtools")
+ require(devtools)
+ }
> install_github(paste0("mi2-warsaw/RTCGA.data/",
+ subdir = paste0("RTCGA.",
+ c("clinical",
+ "rnaseq",
+ "mutations",
+ "cnv",
+ "PANCAN12")
+ )
+ )
+ )
Downloading github repo mi2-warsaw/RTCGA.data#master
Installing RTCGA.clinical
"C:/PROGRA~1/R/R-32~1.0/bin/x64/R" --no-site-file --no-environ \
--no-save --no-restore CMD INSTALL \
"C:/Users/Marcin/AppData/Local/Temp/RtmpeSTVOR/devtoolse483660419b/mi2-warsaw-RTCGA.data-f38f079/RTCGA.clinical" \
--library="C:/Users/Marcin/Documents/R/win-library/3.2" \
--install-tests
* installing *source* package 'RTCGA.clinical' ...
** R
** data
*** moving datasets to lazyload DB
** preparing package for lazy loading
** help
*** installing help indices
** building package indices
** installing vignettes
** testing if installed package can be loaded
*** arch - i386
*** arch - x64
* DONE (RTCGA.clinical)
Downloading github repo mi2-warsaw/RTCGA.data#master
Installing RTCGA.rnaseq
"C:/PROGRA~1/R/R-32~1.0/bin/x64/R" --no-site-file --no-environ \
--no-save --no-restore CMD INSTALL \
"C:/Users/Marcin/AppData/Local/Temp/RtmpeSTVOR/devtoolse4839392db6/mi2-warsaw-RTCGA.data-3c044a0/RTCGA.rnaseq" \
--library="C:/Users/Marcin/Documents/R/win-library/3.2" \
--install-tests
* installing *source* package 'RTCGA.rnaseq' ...
** R
** data
*** moving datasets to lazyload DB
it looks like for each single package's installation the whole repository is downloaded. So in a result the whole repository is downloaded 5 times...
Is there a way to download the repository once, and to install 5 packages then - if possible - in a one function call similar to the one I am using?