From deec78cdd37cb0e2ef7a5748128d6b9870bcdbbb Mon Sep 17 00:00:00 2001
From: ridiculousfish <rf@fishshell.com>
Date: Sat, 6 Aug 2022 12:52:11 -0700
Subject: [PATCH] cmake: Unset GIT_WORK_TREE and GIT_DIR before
 FetchContent_Populate

GIT_WORK_TREE is an environment variable which tells git where the
worktree is. It may be set by the user or by git itself, e.g. when
running `git rebase -i --exec ...`. If it is set, it overrides the
working directory, causing the `git checkout` from FetchContent_Populate
to fail. Clear this variable.

Do the same for GIT_DIR for the same reason.

A way to reproduce the failure that this commit fixes is:

    git rebase -i HEAD^^^ --exec 'ninja -C /path/to/build/dir fish'

prior to this commit, using the fetched PCRE2, this would fail in CMake.
---
 cmake/PCRE2.cmake | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/cmake/PCRE2.cmake b/cmake/PCRE2.cmake
index b9138fe2e..8b3710131 100644
--- a/cmake/PCRE2.cmake
+++ b/cmake/PCRE2.cmake
@@ -54,6 +54,12 @@ else()
   # so we end up installing all of PCRE2 including its headers, man pages, etc.
   FetchContent_GetProperties(pcre2)
   if (NOT pcre2_POPULATED)
+    # If GIT_WORK_TREE is set (by user or by git itself with e.g. git rebase), it
+    # will override the git directory which CMake tries to apply in FetchContent_Populate,
+    # resulting in a failed checkout.
+    # Ensure it is not set.
+    unset(ENV{GIT_WORK_TREE})
+    unset(ENV{GIT_DIR})
     FetchContent_Populate(pcre2)
     add_subdirectory(${pcre2_SOURCE_DIR} ${pcre2_BINARY_DIR} EXCLUDE_FROM_ALL)
   endif()