Add KTX_GIT_VERSION_FULL and update readme

BUILDING.md

@@ -63,6 +63,12 @@ add `-D BASISU_SUPPORT_OPENCL=ON` to the CMake configure command.
 >  There is very little advantage to using OpenCL in the context
 >  of `libktx`. It is disabled in the default build configuration.
 
+> **Note:**
+> 
+> When building from the `tar.gz` and not from the git repository directly, it is recommended to pass the variable `KTX_GIT_VERSION_FULL` with the associated git tag (e.g `v4.3.2`)
+> ```bash
+> cmake . -G Ninja -B build -DKTX_GIT_VERSION_FULL=v4.3.2
+> ```
 
 Building
 --------

cmake/version.cmake

@@ -109,8 +109,9 @@ function(generate_version _var )
 endfunction()
 
 # Get latest tag from git if not passed to cmake
-if(NOT KTX_VERSION_FULL)
-    git_describe_raw(KTX_VERSION_FULL --abbrev=0 --match v[0-9]*)
+# This property can be passed to cmake when building from tar.gz
+if(NOT KTX_GIT_VERSION_FULL)
+    git_describe_raw(KTX_GIT_VERSION_FULL --abbrev=0 --match v[0-9]*)
 endif()
 #message("KTX full version: ${KTX_VERSION_FULL}")
 
@@ -119,7 +120,7 @@ endif()
 
 # First try a full regex ( vMAJOR.MINOR.PATCH-TWEAK )
 string(REGEX MATCH "^v([0-9]*)\.([0-9]*)\.([0-9]*)(-[^\.]*)"
-       KTX_VERSION ${KTX_VERSION_FULL})
+       KTX_VERSION ${KTX_GIT_VERSION_FULL})
 
 if(KTX_VERSION)
     set(KTX_VERSION_MAJOR ${CMAKE_MATCH_1})
@@ -129,7 +130,7 @@ if(KTX_VERSION)
 else()
     # If full regex failed, go for vMAJOR.MINOR.PATCH
     string(REGEX MATCH "^v([0-9]*)\.([0-9]*)\.([^\.]*)"
-            KTX_VERSION ${KTX_VERSION_FULL})
+            KTX_VERSION ${KTX_GIT_VERSION_FULL})
 
     if(KTX_VERSION)
         set(KTX_VERSION_MAJOR ${CMAKE_MATCH_1})
@@ -176,15 +177,15 @@ function( create_version_header dest_path target )
         add_custom_command(
             OUTPUT ${version_h_output}
             # On Windows this command has to be invoked by a shell in order to work
-            COMMAND ${BASH_EXECUTABLE} -c "\"scripts/mkversion\" \"-v\" \"${KTX_VERSION_FULL}\" \"-o\" \"version.h\" \"${dest_path}\""
+            COMMAND ${BASH_EXECUTABLE} -c "\"scripts/mkversion\" \"-v\" \"${KTX_GIT_VERSION_FULL}\" \"-o\" \"version.h\" \"${dest_path}\""
             WORKING_DIRECTORY ${PROJECT_SOURCE_DIR}
             COMMENT "Generate ${version_h_output}"
             VERBATIM
         )
     else()
         add_custom_command(
             OUTPUT ${version_h_output}
-            COMMAND scripts/mkversion -v ${KTX_VERSION_FULL} -o version.h ${dest_path}
+            COMMAND scripts/mkversion -v ${KTX_GIT_VERSION_FULL} -o version.h ${dest_path}
             WORKING_DIRECTORY ${PROJECT_SOURCE_DIR}
             COMMENT "Generate ${version_h_output}"
             VERBATIM