platform_manifest_twrp_omni/twrp-extras.xml

<?xml version="1.0" encoding="UTF-8"?>
<manifest>
    <remote name="TeamWin"
            fetch="https://github.com/TeamWin"
            review="https://gerrit.twrp.me" />

    <remote name="LineageOS"
            fetch="https://github.com/LineageOS"
            review="https://review.lineageos.org" />

<!-- TWRP lives in TeamWin repo, not AOSP -->
    <remove-project name="platform/bootable/recovery" />
    <project path="bootable/recovery" name="android_bootable_recovery" remote="TeamWin" revision="android-9.0" />

<!-- Use TeamWin fork for repacker support -->
  <remove-project name="android_build" />
  <project path="build/make" name="android_build" remote="TeamWin" revision="android-8.1" groups="pdk" >
    <copyfile src="core/root.mk" dest="Makefile" />
    <linkfile src="CleanSpec.mk" dest="build/CleanSpec.mk" />
    <linkfile src="buildspec.mk.default" dest="build/buildspec.mk.default" />
    <linkfile src="core" dest="build/core" />
    <linkfile src="envsetup.sh" dest="build/envsetup.sh" />
    <linkfile src="target" dest="build/target" />
    <linkfile src="tools" dest="build/tools" />
  </project>

<!-- Use OmniROM busybox -->
    <project path="external/busybox" name="android_external_busybox" remote="omnirom" revision="android-8.1" />

<!-- Use TeamWin repos as Omni doesn't accept any updates for recovery purposes -->
    <project path="vendor/omni" name="android_vendor_omni" remote="TeamWin" revision="android-8.1" />

<!-- Use TeamWin boringssl repo - needed for arm devices requiring entropy for decryption -->
    <remove-project name="platform/external/boringssl" />
    <project path="external/boringssl" name="external_boringssl" remote="TeamWin" revision="android-8.1" />

<!-- Include external Magisk repo for repack binaries -->
    <project path="external/magisk-prebuilt" name="external_magisk-prebuilt" remote="TeamWin" revision="android-8.1" />

    <project path="external/python3" name="android_external_python3" remote="TeamWin" revision="android-9.0"/>

<!-- Include TeamWin android_system_update_engine to build a good update_engine_sideload -->
    <remove-project name="android_system_update_engine" />
    <project path="system/update_engine" name="android_system_update_engine" remote="TeamWin" revision="android-8.1" />

<!-- Include shallow clone of needed external/frameworks folders -->
    <project path="external/nist-sip" name="platform/external/nist-sip" groups="pdk" clone-depth="1" />
    <project path="external/tagsoup" name="platform/external/tagsoup" groups="pdk" clone-depth="1" />
    <project path="frameworks/base" name="android_frameworks_base" remote="omnirom" revision="android-8.1" clone-depth="1" />
    <project path="frameworks/data-binding" name="platform/frameworks/data-binding" groups="pdk-cw-fs,pdk-fs" clone-depth="1" />
    <project path="frameworks/opt/net/voip" name="platform/frameworks/opt/net/voip" groups="pdk-cw-fs,pdk-fs" clone-depth="1" />
    <project path="frameworks/opt/telephony" name="android_frameworks_opt_telephony" remote="omnirom" revision="android-8.1" clone-depth="1" />
    <project path="frameworks/support" name="platform/frameworks/support" groups="pdk-cw-fs,pdk-fs" clone-depth="1" />

<!-- Include external LineageOS repos for bash & nano -->
    <project name="android_external_bash" path="external/bash" remote="LineageOS" revision="lineage-15.1" />
    <project name="android_external_nano" path="external/nano" remote="LineageOS" revision="lineage-15.1" />
    <project name="android_external_libncurses" path="external/libncurses" remote="LineageOS" revision="lineage-15.1" />
</manifest>