Update to 2.38.0. From the changelog:

- INSTALL.md: correct a filename with mixed underscore and dash
- filter-repo: prepend the header line to the "ref-map" file
- Makefile: support DESTDIR
- doc: fix some typos
- Update expected test data for git 2.35
- git-filter-repo.txt: add missing git- prefix to fast-import link
- git-filter-repo.txt: fix small grammar error
- clean-ignore: move commands under main function
- clean-ignore: use arguments provided as input instead of enforced defaults
- lint-history: Add --refs argument
- Correct mailmapping of empty email addresses
- lint-history: fix broken --refs option
- contrib: new tool to convert svn:externals to Git submodules
- filter-repo: pass raw bytestring to regex compilation

(schmonz)