update git_tags to handle the case where there are no labels in the repo (#1906)

cmake/Modules/git_tags.cmake

@@ -20,7 +20,8 @@ function(NGRAPH_GET_CURRENT_HASH)
         COMMAND ${GIT_EXECUTABLE} rev-parse --verify HEAD
         RESULT_VARIABLE result
         OUTPUT_VARIABLE HASH
-        WORKING_DIRECTORY ${CMAKE_SOURCE_DIR})
+        WORKING_DIRECTORY ${CMAKE_SOURCE_DIR}
+        ERROR_QUIET)
 
     string(STRIP ${HASH} HASH)
     set(NGRAPH_CURRENT_HASH ${HASH} PARENT_SCOPE)
@@ -32,15 +33,20 @@ function(NGRAPH_GET_TAG_OF_CURRENT_HASH)
         COMMAND ${GIT_EXECUTABLE} ls-remote --tags
         RESULT_VARIABLE RESULT
         OUTPUT_VARIABLE TAG_LIST
-        WORKING_DIRECTORY ${CMAKE_SOURCE_DIR})
+        WORKING_DIRECTORY ${CMAKE_SOURCE_DIR}
+        ERROR_QUIET)
 
     NGRAPH_GET_CURRENT_HASH()
 
+    if (NOT ${TAG_LIST} STREQUAL "")
         string(REGEX MATCH "${NGRAPH_CURRENT_HASH}\t[^\r\n]*" TAG ${TAG_LIST})
         set(FINAL_TAG ${TAG})
         if (NOT "${TAG}" STREQUAL "")
             string(REGEX REPLACE "${NGRAPH_CURRENT_HASH}\trefs/tags/(.*)" "\\1" FINAL_TAG ${TAG})
         endif()
+    else()
+        set(FINAL_TAG "")
+    endif()
     set(NGRAPH_CURRENT_RELEASE_TAG ${FINAL_TAG} PARENT_SCOPE)
 endfunction()
 
@@ -50,9 +56,12 @@ function(NGRAPH_GET_MOST_RECENT_TAG)
         COMMAND ${GIT_EXECUTABLE} describe --tags --abbrev=0
         RESULT_VARIABLE RESULT
         OUTPUT_VARIABLE TAG
-        WORKING_DIRECTORY ${CMAKE_SOURCE_DIR})
+        WORKING_DIRECTORY ${CMAKE_SOURCE_DIR}
+        ERROR_QUIET)
 
+    if (NOT ${TAG} STREQUAL "")
         string(STRIP ${TAG} TAG)
+    endif()
     set(NGRAPH_MOST_RECENT_RELEASE_TAG ${TAG} PARENT_SCOPE)
 endfunction()
 
@@ -63,6 +72,10 @@ function(NGRAPH_GET_VERSION_LABEL)
         NGRAPH_GET_CURRENT_HASH()
         NGRAPH_GET_MOST_RECENT_TAG()
         string(SUBSTRING "${NGRAPH_CURRENT_HASH}" 0 7 HASH)
+        if (NOT ${NGRAPH_MOST_RECENT_RELEASE_TAG} STREQUAL "")
             set(NGRAPH_VERSION_LABEL "${NGRAPH_MOST_RECENT_RELEASE_TAG}+${HASH}" PARENT_SCOPE)
+        else()
+            set(NGRAPH_VERSION_LABEL "?.?.?+${HASH}" PARENT_SCOPE)
+        endif()
     endif()
 endfunction()