Broken cmake caching

Apparently libgit2 repo contains conflicting installs in src/libgit2/CMakeLists.txt.

The first line https://github.com/libgit2/libgit2/blob/main/src/libgit2/CMakeLists.txt#L135 installs a placeholder file ${PROJECT_SOURCE_DIR}/include/git2/experimental.h and then second https://github.com/libgit2/libgit2/blob/main/src/libgit2/CMakeLists.txt#L137 overrides it with the generated version ${PROJECT_BINARY_DIR}/include/git2/experimental.h.

# src/libgit2/CMakeLists.txt
L135: install(DIRECTORY ${PROJECT_SOURCE_DIR}/include/git2/
L136:        DESTINATION "${CMAKE_INSTALL_INCLUDEDIR}/${LIBGIT2_FILENAME}")
L137: install(FILES ${PROJECT_BINARY_DIR}/include/git2/experimental.h
L138:        DESTINATION "${CMAKE_INSTALL_INCLUDEDIR}/${LIBGIT2_FILENAME}")

This nullifies cmake cache (please find repeated Installing lines below) and forces a rebuild of dependent projects.

-- Up-to-date: /Users/dimatcimbal/code/libgit2/installdir/include/git2/refs.h
-- Up-to-date: /Users/dimatcimbal/code/libgit2/installdir/include/git2/reset.h
-- Up-to-date: /Users/dimatcimbal/code/libgit2/installdir/include/git2/filter.h
-- Up-to-date: /Users/dimatcimbal/code/libgit2/installdir/include/git2/transaction.h
-- Installing: /Users/dimatcimbal/code/libgit2/installdir/include/git2/experimental.h
-- Up-to-date: /Users/dimatcimbal/code/libgit2/installdir/include/git2/stdint.h
-- Up-to-date: /Users/dimatcimbal/code/libgit2/installdir/include/git2/commit.h
-- Up-to-date: /Users/dimatcimbal/code/libgit2/installdir/include/git2/refdb.h
-- Installing: /Users/dimatcimbal/code/libgit2/installdir/include/git2/experimental.h
-- Up-to-date: /Users/dimatcimbal/code/libgit2/installdir/include/git2.h
-- Up-to-date: /Users/dimatcimbal/code/libgit2/installdir/bin/git2

The fix: https://github.com/libgit2/libgit2/pull/7109

Read src/libgit2/CMakeLists.txt around lines 135-138 and compare the source and generated experimental.h install entries. Reproduce the repeated Installing output from the issue, then verify installation no longer reports duplicate work and dependent projects are not forced to rebuild; PR 7109 is cited as the fix.