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externals/vcpkg/docs/maintainers/vcpkg_from_github.md

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+# vcpkg_from_github
+
+The latest version of this document lives in the [vcpkg repo](https://github.com/Microsoft/vcpkg/blob/master/docs/maintainers/vcpkg_from_github.md).
+
+Download and extract a project from GitHub. Enables support for `install --head`.
+
+This also works with Gitea by specifying the Gitea server with the `GITHUB_HOST` option.
+
+## Usage:
+```cmake
+vcpkg_from_github(
+    OUT_SOURCE_PATH <SOURCE_PATH>
+    REPO <Microsoft/cpprestsdk>
+    [REF <v2.0.0>]
+    [SHA512 <45d0d7f8cc350...>]
+    [HEAD_REF <master>]
+    [PATCHES <patch1.patch> <patch2.patch>...]
+    [GITHUB_HOST <https://github.com>]
+    [AUTHORIZATION_TOKEN <${SECRET_FROM_FILE}>]
+    [FILE_DISAMBIGUATOR <N>]
+)
+```
+
+## Parameters:
+### OUT_SOURCE_PATH
+Specifies the out-variable that will contain the extracted location.
+
+This should be set to `SOURCE_PATH` by convention.
+
+### REPO
+The organization or user and repository on GitHub.
+
+### REF
+A stable git commit-ish (ideally a tag or commit) that will not change contents. **This should not be a branch.**
+
+For repositories without official releases, this can be set to the full commit id of the current latest master.
+
+If `REF` is specified, `SHA512` must also be specified.
+
+### SHA512
+The SHA512 hash that should match the archive (https://github.com/${REPO}/archive/${REF}.tar.gz).
+
+This is most easily determined by first setting it to `0`, then trying to build the port. The error message will contain the full hash, which can be copied back into the portfile.
+
+### HEAD_REF
+The unstable git commit-ish (ideally a branch) to pull for `--head` builds.
+
+For most projects, this should be `master`. The chosen branch should be one that is expected to be always buildable on all supported platforms.
+
+### PATCHES
+A list of patches to be applied to the extracted sources.
+
+Relative paths are based on the port directory.
+
+### GITHUB_HOST
+A replacement host for enterprise GitHub instances.
+
+This field should contain the scheme, host, and port of the desired URL without a trailing slash.
+
+### AUTHORIZATION_TOKEN
+A token to be passed via the Authorization HTTP header as "token ${AUTHORIZATION_TOKEN}".
+
+### FILE_DISAMBIGUATOR
+A token to uniquely identify the resulting filename if the SHA512 changes even though a git ref does not, to avoid stepping on the same file name.
+
+## Notes:
+At least one of `REF` and `HEAD_REF` must be specified, however it is preferable for both to be present.
+
+This exports the `VCPKG_HEAD_VERSION` variable during head builds.
+
+## Examples:
+
+* [cpprestsdk](https://github.com/Microsoft/vcpkg/blob/master/ports/cpprestsdk/portfile.cmake)
+* [ms-gsl](https://github.com/Microsoft/vcpkg/blob/master/ports/ms-gsl/portfile.cmake)
+* [boost-beast](https://github.com/Microsoft/vcpkg/blob/master/ports/boost-beast/portfile.cmake)
+
+## Source
+[scripts/cmake/vcpkg\_from\_github.cmake](https://github.com/Microsoft/vcpkg/blob/master/scripts/cmake/vcpkg_from_github.cmake)