Implement the git short commit SHA1, using git rev-parse --short

Author: Alessandro Bertulli

git.c.in

@@ -30,3 +30,6 @@ const char* git_Describe() {
 const char* git_Branch() {
     return "@GIT_BRANCH@";
 }
+const char* git_CommitShort() {
+    return "@GIT_SHORT@";
+}

git.h

@@ -52,6 +52,9 @@ const char* git_Describe();
 /// The symbolic reference tied to HEAD.
 const char* git_Branch();
 
+/// The commit short SHA1.
+const char* git_CommitShort();
+
 GIT_VERSION_TRACKING_EXTERN_C_END
 #undef GIT_VERSION_TRACKING_EXTERN_C_BEGIN
 #undef GIT_VERSION_TRACKING_EXTERN_C_END
@@ -143,6 +146,10 @@ inline const StringOrView Branch() {
   static const StringOrView kValue = internal::InitString(git_Branch());
   return kValue;
 }
+inline const StringOrView CommitShort() {
+  static const StringOrView kValue = internal::InitString(git_CommitShort());
+  return kValue;
+}
 
 }  // namespace git
 

git_watcher.cmake

@@ -105,6 +105,7 @@ set(_state_variable_names
     GIT_COMMIT_BODY
     GIT_DESCRIBE
     GIT_BRANCH
+    GIT_SHORT
     # >>>
     # 1. Add the name of the additional git variable you're interested in monitoring
     #    to this list.
@@ -242,6 +243,14 @@ function(GetGitState _working_dir)
         set(ENV{GIT_BRANCH} "${output}")
     endif()
 
+    # Get output of git describe
+    RunGitCommand(rev-parse --short ${object})
+    if(NOT exit_code EQUAL 0)
+        set(ENV{GIT_SHORT} "unknown")
+    else()
+        set(ENV{GIT_SHORT} "${output}")
+    endif()
+
     # >>>
     # 2. Additional git properties can be added here via the
     #    "execute_process()" command. Be sure to set them in