version: generate "build number" from commit timestamp

- cmake: git_timestamp() returns last commit time formatted as
  `YYYYMMddHHmm`.
- Always include commit hash in :version and --version output.

`nvim --version` sample output:
  NVIM 0.0.0-alpha+201410070245 (compiled Oct  7 2014 05:30:45)
  Commit: f747b2b1ff7bfe7eb00cc2be82d7af87c98f1111

CMakeLists.txt

@@ -12,14 +12,17 @@ set(DEPS_BIN_DIR "${DEPS_INSTALL_DIR}/bin")
 
 list(APPEND CMAKE_PREFIX_PATH ${DEPS_INSTALL_DIR})
 
+# Version tokens
 include(GetGitRevisionDescription)
-get_git_head_revision(GIT_REFSPEC GIT_SHA1)
+get_git_head_revision(GIT_REFSPEC NVIM_VERSION_COMMIT)
 set(NVIM_VERSION_MAJOR 0)
 set(NVIM_VERSION_MINOR 0)
 set(NVIM_VERSION_PATCH 0)
 set(NVIM_VERSION_PRERELEASE "-alpha")
+# TODO(justinmk): UTC time would be nice here #1071
+git_timestamp(GIT_TIMESTAMP)
 # TODO(justinmk): do not set this for "release" builds #1071
-set(NVIM_VERSION_BUILD "+${GIT_SHA1}")
+set(NVIM_VERSION_BUILD "+${GIT_TIMESTAMP}")
 
 set(CMAKE_EXPORT_COMPILE_COMMANDS ON)
 

cmake/GetGitRevisionDescription.cmake

@@ -126,6 +126,35 @@ function(git_describe _var)
   set(${_var} "${out}" PARENT_SCOPE)
 endfunction()
 
+function(git_timestamp _var)
+  if(NOT GIT_FOUND)
+    find_package(Git QUIET)
+  endif()
+  get_git_head_revision(refspec hash)
+  if(NOT GIT_FOUND)
+    set(${_var} "GIT-NOTFOUND" PARENT_SCOPE)
+    return()
+  endif()
+  if(NOT hash)
+    set(${_var} "HEAD-HASH-NOTFOUND" PARENT_SCOPE)
+    return()
+  endif()
+
+  execute_process(COMMAND "${GIT_EXECUTABLE}" log -1 --format="%ci" ${hash} ${ARGN}
+    WORKING_DIRECTORY "${CMAKE_SOURCE_DIR}"
+    RESULT_VARIABLE res
+    OUTPUT_VARIABLE out
+    ERROR_QUIET
+    OUTPUT_STRIP_TRAILING_WHITESPACE)
+  if(NOT res EQUAL 0)
+    set(out "${out}-${res}-NOTFOUND")
+  endif()
+  string(REGEX REPLACE "[-\" :]" "" out ${out})
+  string(SUBSTRING ${out} 0 12 out)
+
+  set(${_var} ${out} PARENT_SCOPE)
+endfunction()
+
 function(git_get_exact_tag _var)
   git_describe(out --exact-match ${ARGN})
   set(${_var} "${out}" PARENT_SCOPE)

config/config.h.in

@@ -3,6 +3,7 @@
 #define NVIM_VERSION_PATCH @NVIM_VERSION_PATCH@
 #define NVIM_VERSION_PRERELEASE "@NVIM_VERSION_PRERELEASE@"
 #define NVIM_VERSION_BUILD "@NVIM_VERSION_BUILD@"
+#define NVIM_VERSION_COMMIT "@NVIM_VERSION_COMMIT@"
 
 #cmakedefine DEBUG
 

src/nvim/version.c

@@ -18,9 +18,8 @@
 #include "nvim/version_defs.h"
 
 char *Version = VIM_VERSION_SHORT;
-
-char *longVersion = NVIM_VERSION_LONG_DATE __DATE__ " " __TIME__ ")";
-
+char *longVersion = NVIM_VERSION_LONG " (compiled " __DATE__ " " __TIME__ ")";
+char *version_commit = "Commit: " NVIM_VERSION_COMMIT;
 
 #ifdef INCLUDE_GENERATED_DECLARATIONS
 # include "version.c.generated.h"
@@ -747,6 +746,7 @@ void list_version(void)
   // When adding features here, don't forget to update the list of
   // internal variables in eval.c!
   MSG(longVersion);
+  MSG(version_commit);
 
   // Print the list of extra patch descriptions if there is at least one.
   char *s = "";

src/nvim/version_defs.h

@@ -27,11 +27,13 @@
 #ifndef NVIM_VERSION_BUILD
 #define NVIM_VERSION_BUILD
 #endif
+#ifndef NVIM_VERSION_COMMIT
+#define NVIM_VERSION_COMMIT
+#endif
 // for the startup-screen
 #define NVIM_VERSION_MEDIUM STR(NVIM_VERSION_MAJOR) "." STR(NVIM_VERSION_MINOR)
 // for the ":version" command and "nvim -h"
 #define NVIM_VERSION_LONG "NVIM " NVIM_VERSION_MEDIUM "." STR(NVIM_VERSION_PATCH) NVIM_VERSION_PRERELEASE NVIM_VERSION_BUILD
-#define NVIM_VERSION_LONG_DATE NVIM_VERSION_LONG " (compiled "
 
 //
 // Vim version number, name, etc. Patchlevel is defined in version.c.