read baseline commit from manifest and checkout specified vcpkg version

README.md

@@ -47,7 +47,7 @@ When a `vcpkg.json` manifest file is present, all packages from this manifest wi
 cmake -DVCPKG_PARENT_DIR=<path-to-build-directory> -P <path-to>/vcpkg.cmake
 ```
 * **Set your build directory** using `-DVCPKG_PARENT_DIR=<path-to-build-directory>` (directory will be created if not exists)
-* Set your *vcpkg* version as outlined below in ***vcpkg* versions** (`-DVCPKG_VERSION=<version>`)
+* if your manifest has no `builtin-baseline`, set your *vcpkg* version as outlined below in ***vcpkg* versions** (`-DVCPKG_VERSION=<version>`)
 * `VCPKG_TARGET_TRIPLET`/`VCPKG_DEFAULT_TRIPLET` CMake variables will set `ENV{VCPKG_DEFAULT_TRIPLET}`
 * `VCPKG_HOST_TRIPLET`/`VCPKG_DEFAULT_HOST_TRIPLET` CMake variables will set `ENV{VCPKG_DEFAULT_HOST_TRIPLET}`
 
@@ -71,6 +71,8 @@ Valid values for `<version>` are:
 * `<empty>`: gets you `latest`
 * `edge`: latest commit on *vcpkg* master branch
 * `<commit-hash>/<tag>`: any tag or commit hash from the *vcpkg*-repo may be used
+
+> 📌 if a `vcpkg.json` manifest exists and specifies a `builtin-baseline`, this commit will be checked out
   
 
 ## setting target/host architecture

vcpkg.cmake

@@ -286,7 +286,6 @@ endfunction()
 
 # determine git checkout target in: VCPKG_VERSION_CHECKOUT
 # vcpkg_set_version_checkout([VCPKG_VERSION_EXPLICIT] [VCPKG_DIRECTORY_EXPLICIT])
-# TODO: set hash from vcpkg.json manifest if version==""
 function(vcpkg_set_version_checkout)
     if(ARGV0 EQUAL "" OR NOT DEFINED ARGV0)
         set(VCPKG_VERSION_EXPLICIT ${VCPKG_VERSION})
@@ -304,6 +303,30 @@ function(vcpkg_set_version_checkout)
     string(REGEX REPLACE "\n$" "" VCPKG_GIT_TAG_LATEST "${VCPKG_GIT_TAG_LATEST}")
 
     # resolve versions
+    if(EXISTS "./vcpkg.json")
+        # set hash from vcpkg.json manifest
+        file(READ "./vcpkg.json" VCPKG_MANIFEST_CONTENTS)
+
+        if(CMAKE_VERSION VERSION_GREATER_EQUAL 3.19)
+            string(JSON VCPKG_BASELINE GET "${VCPKG_MANIFEST_CONTENTS}" "builtin-baseline")
+        else()
+            string(REGEX REPLACE "[\n ]" "" VCPKG_MANIFEST_CONTENTS "${VCPKG_MANIFEST_CONTENTS}")
+            message(STATUS "manifest: ${VCPKG_MANIFEST_CONTENTS}")
+            string(REGEX MATCH "\"builtin-baseline\":\"[0-9a-f]+\"" VCPKG_BASELINE "${VCPKG_MANIFEST_CONTENTS}")
+            string(REPLACE "\"builtin-baseline\":" "" VCPKG_BASELINE "${VCPKG_BASELINE}")
+            string(REPLACE "\"" "" VCPKG_BASELINE "${VCPKG_BASELINE}")
+            message(STATUS "basline commit: ${VCPKG_BASELINE}")
+        endif()
+
+        if(NOT "${VCPKG_BASELINE}" EQUAL "")
+            if(NOT "${VCPKG_VERSION}" EQUAL "" AND DEFINED VCPKG_VERSION)
+                message(WARNING "VCPKG_VERSION was specified, but vcpkg.json manifest is used and specifies a builtin-baseline; using builtin-baseline: ${VCPKG_BASELINE}")
+            endif()
+            set(VCPKG_VERSION_EXPLICIT "${VCPKG_BASELINE}")
+            message(STATUS "Using VCPKG Version: <manifest builtin-baseline>")
+        endif()
+    endif()
+
     if("${VCPKG_VERSION_EXPLICIT}" STREQUAL "latest" OR "${VCPKG_VERSION_EXPLICIT}" EQUAL "" OR NOT DEFINED VCPKG_VERSION_EXPLICIT)
         set(VCPKG_VERSION_CHECKOUT ${VCPKG_GIT_TAG_LATEST})
         message(STATUS "Using VCPKG Version: ${VCPKG_VERSION_EXPLICIT} (latest)")