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externals/vcpkg/docs/maintainers/vcpkg_from_gitlab.md

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+# vcpkg_from_gitlab
+
+The latest version of this document lives in the [vcpkg repo](https://github.com/Microsoft/vcpkg/blob/master/docs/maintainers/vcpkg_from_gitlab.md).
+
+Download and extract a project from Gitlab instances. Enables support for `install --head`.
+
+## Usage:
+```cmake
+vcpkg_from_gitlab(
+    GITLAB_URL <https://gitlab.com>
+    OUT_SOURCE_PATH <SOURCE_PATH>
+    REPO <gitlab-org/gitlab-ce>
+    [REF <v10.7.3>]
+    [SHA512 <45d0d7f8cc350...>]
+    [HEAD_REF <master>]
+    [PATCHES <patch1.patch> <patch2.patch>...]
+    [FILE_DISAMBIGUATOR <N>]
+)
+```
+
+## Parameters:
+
+### GITLAB_URL
+The URL of the Gitlab instance to use.
+
+### 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 plus the repository name on the Gitlab instance.
+
+### REF
+A stable git commit-ish (ideally a tag) 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 (${GITLAB_URL}/${REPO}/-/archive/${REF}/${REPO_NAME}-${REF}.tar.gz).
+The REPO_NAME variable is parsed from the value of REPO.
+
+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.
+
+### 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:
+* [curl][https://github.com/Microsoft/vcpkg/blob/master/ports/curl/portfile.cmake#L75]
+* [folly](https://github.com/Microsoft/vcpkg/blob/master/ports/folly/portfile.cmake#L15)
+* [z3](https://github.com/Microsoft/vcpkg/blob/master/ports/z3/portfile.cmake#L13)
+
+## Source
+[scripts/cmake/vcpkg\_from\_gitlab.cmake](https://github.com/Microsoft/vcpkg/blob/master/scripts/cmake/vcpkg_from_gitlab.cmake)