* guix/build/git.scm (git-fetch-with-fallback): Add #:hash
and #:hash-algorithm. Try ‘swh-download-directory-by-nar-hash’ before
‘swh-download’ when #:hash is provided.
* guix/git-download.scm (git-fetch/in-band*): Pass #:hash
and #:hash-algorithm to ‘git-fetch-with-fallback’.
* guix/scripts/perform-download.scm (perform-git-download): Likewise.
Change-Id: Ic875a7022fd78c9fac32e92ad4f8ce4d81646ec5