Improvements in the package installation feature.

Support for yum and avoid caching of INSTALL_PACKAGES in CMakeCache.txt.
This changes are motivated by some issues reported by a user trying
to compile Equalizer in RHEL.

CHANGES.md

@@ -1,3 +1,10 @@
+# git master
+
+* [504](https://github.com/Eyescale/CMake/pull/504):
+    * Add support for yum to subproject_install_packages
+    * Make sure that package installation is only attempted if INSTALL_PACKAGES
+      is in the command line (i.e. do not cache the variable).
+
 # 2016.06 (30-Jun-2016)
 
 * [503](https://github.com/Eyescale/CMake/pull/503):

CommonFindPackage.cmake

@@ -269,4 +269,8 @@ macro(common_find_package_post)
   endif()
   common_graph(${PROJECT_NAME})
   message(STATUS ${__configure_msg})
+
+  # If this variable was given in the command line, ensure that the package
+  # installation is only run in this cmake invocation.
+  unset(INSTALL_PACKAGES CACHE)
 endmacro()

README.md

@@ -78,6 +78,9 @@ The following CMake modules can be included in your project:
 
 Additional features:
 * Users can use "cmake -DINSTALL_PACKAGES=1" during the initial configuration to
-  install known system packages (Ubuntu and OS X only).
+  install known system packages.
+  This is only implemented for Linux distributions using apt-get and yum
+  package managers and MacPorts in OS X. The actual support depends on the
+  project declaring its dependencies for each particular case.
 
 [Detailed Change Log](CHANGES.md)

SubProject.cmake

@@ -80,12 +80,33 @@ function(subproject_install_packages name)
     clang-format-3.5) # optional deb packages, not added to build spec
   list(APPEND ${NAME}_PORT_DEPENDS cppcheck)
 
-  if(${NAME}_DEB_DEPENDS AND CMAKE_SYSTEM_NAME MATCHES "Linux" )
-    list(SORT ${NAME}_DEB_DEPENDS)
-    list(REMOVE_DUPLICATES ${NAME}_DEB_DEPENDS)
-    message("Running 'sudo apt-get install ${${NAME}_DEB_DEPENDS}'")
-    execute_process(COMMAND sudo apt-get install ${${NAME}_DEB_DEPENDS})
+  if(CMAKE_SYSTEM_NAME MATCHES "Linux" )
+    # Detecting the package manager to use
+    find_program(__pkg_mng apt-get)
+    if(__pkg_mng)
+      set(__pkg_type DEB)
+    elseif(__pkg_mng)
+      find_program(__pkg_mng yum)
+      if(__pkg_mng)
+        set(__pkg_type RPM)
+      endif()
+    endif()
+    if(NOT __pkg_mng)
+      message(WARNING "Could not determine the package manager for installing dependencies")
+      # Removing INSTALL_PACKAGES so the warning is not printed repeatedly.
+      unset(INSTALL_PACKAGES CACHE)
+    endif()
+
+    if(__pkg_mng AND ${NAME}_${__pkg_type}_DEPENDS)
+      list(SORT ${NAME}_${__pkg_type}_DEPENDS)
+      list(REMOVE_DUPLICATES ${NAME}_${__pkg_type}_DEPENDS)
+      message(
+        "Running 'sudo ${__pkg_mng} install ${${NAME}_${__pkg_type}_DEPENDS}'")
+      execute_process(
+          COMMAND sudo ${__pkg_mng} install ${${NAME}_${__pkg_type}_DEPENDS})
+    endif()
   endif()
+
   if(${NAME}_PORT_DEPENDS AND APPLE)
     list(SORT ${NAME}_PORT_DEPENDS)
     list(REMOVE_DUPLICATES ${NAME}_PORT_DEPENDS)