无法在centOS 7.0 64位上安装git2r或devtools R软件包

我R在centOS下安装软件包失败。我正在尝试安装该devtools软件包，以便rstudio/DT使用该install_github功能安装该软件包，但是当我尝试安装该devtools软件包时，出现以下错误，提示git2r无法安装该软件包。也许有人知道我应该怎么做才能成功执行安装？

我的代码和错误sessionInfo如下：

also installing the dependency ‘git2r’

próbowanie adresu URL 'http://r.meteo.uni.wroc.pl/src/contrib/git2r_0.10.1.tar.gz'
Content type 'application/x-gzip' length 1014817 bytes (991 Kb)
otwarty adres URL
==================================================
downloaded 991 Kb

próbowanie adresu URL 'http://r.meteo.uni.wroc.pl/src/contrib/devtools_1.8.0.tar.gz'
Content type 'application/x-gzip' length 141487 bytes (138 Kb)
otwarty adres URL
==================================================
downloaded 138 Kb

* installing *source* package ‘git2r’ ...
** pakiet ‘git2r’ został pomyślnie rozpakowany oraz sumy MD5 zostały sprawdzone
checking build system type... x86_64-unknown-linux-gnu
checking host system type... x86_64-unknown-linux-gnu
checking for gcc... gcc
checking whether the C compiler works... yes
checking for C compiler default output file name... a.out
checking for suffix of executables... 
checking whether we are cross compiling... no
checking for suffix of object files... o
checking whether we are using the GNU C compiler... yes
checking whether gcc accepts -g... yes
checking for gcc option to accept ISO C89... none needed
checking for library containing inflate... -lz
checking for library containing SSL_library_init... no
configure: error: in `/tmp/Rtmpu69dSw/R.INSTALL78eb79d3960d/git2r':
configure: error: OpenSSL library required
See `config.log' for more details
ERROR: configuration failed for package ‘git2r’
* removing ‘/usr/lib64/R/library/git2r’
ERROR: dependency ‘git2r’ is not available for package ‘devtools’
* removing ‘/usr/lib64/R/library/devtools’

Pobrane pakiety źródłowe są w
    ‘/tmp/RtmpPa6Dam/downloaded_packages’
Aktualizowanie indeksu HTML pakietów w '.Library'
Making 'packages.html' ... wykonano
Komunikaty ostrzegawcze:
1: In install.packages("devtools") :
  instalacja pakietu ‘git2r’ miała niezerowy status wyjścia
2: In install.packages("devtools") :
  instalacja pakietu ‘devtools’ miała niezerowy status wyjścia
> install.packages("git2r")
Installing package into ‘/usr/lib64/R/library’
(as ‘lib’ is unspecified)
próbowanie adresu URL 'http://r.meteo.uni.wroc.pl/src/contrib/git2r_0.10.1.tar.gz'
Content type 'application/x-gzip' length 1014817 bytes (991 Kb)
otwarty adres URL
==================================================
downloaded 991 Kb

* installing *source* package ‘git2r’ ...
** pakiet ‘git2r’ został pomyślnie rozpakowany oraz sumy MD5 zostały sprawdzone
checking build system type... x86_64-unknown-linux-gnu
checking host system type... x86_64-unknown-linux-gnu
checking for gcc... gcc
checking whether the C compiler works... yes
checking for C compiler default output file name... a.out
checking for suffix of executables... 
checking whether we are cross compiling... no
checking for suffix of object files... o
checking whether we are using the GNU C compiler... yes
checking whether gcc accepts -g... yes
checking for gcc option to accept ISO C89... none needed
checking for library containing inflate... -lz
checking for library containing SSL_library_init... no
configure: error: in `/tmp/Rtmp7XPNF2/R.INSTALL7a40466f8127/git2r':
configure: error: OpenSSL library required
See `config.log' for more details
ERROR: configuration failed for package ‘git2r’
* removing ‘/usr/lib64/R/library/git2r’

Pobrane pakiety źródłowe są w
    ‘/tmp/RtmpPa6Dam/downloaded_packages’
Aktualizowanie indeksu HTML pakietów w '.Library'
Making 'packages.html' ... wykonano
Komunikat ostrzegawczy:
In install.packages("git2r") :
  instalacja pakietu ‘git2r’ miała niezerowy status wyjścia
> sessionInfo(
+ )
R version 3.1.2 (2014-10-31)
Platform: x86_64-redhat-linux-gnu (64-bit)

locale:
 [1] LC_CTYPE=pl_PL.UTF-8       LC_NUMERIC=C              
 [3] LC_TIME=pl_PL.UTF-8        LC_COLLATE=pl_PL.UTF-8    
 [5] LC_MONETARY=pl_PL.UTF-8    LC_MESSAGES=pl_PL.UTF-8   
 [7] LC_PAPER=pl_PL.UTF-8       LC_NAME=C                 
 [9] LC_ADDRESS=C               LC_TELEPHONE=C            
[11] LC_MEASUREMENT=pl_PL.UTF-8 LC_IDENTIFICATION=C       

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base     

loaded via a namespace (and not attached):
[1] tools_3.1.2