I wanted to import an old GNU arch repository into Git, but only had HTTP access via ArchZoom. I spent quite some time to try teaching git archimport to use HTTP access to that repository, but this didn't work out. Too bad -- but at least, using ArchZoom, I was able to get the individual revisions' tarballs:

$ ls -1 *.tar.gz
bpf--devel--0.0--base-0.tar.gz
bpf--devel--0.0--patch-1.tar.gz
bpf--devel--0.0--patch-10.tar.gz
bpf--devel--0.0--patch-11.tar.gz
bpf--devel--0.0--patch-12.tar.gz
bpf--devel--0.0--patch-2.tar.gz
bpf--devel--0.0--patch-3.tar.gz
[...]
bpf--devel--0.0--patch-9.tar.gz
bpf--release--0.1--base-0.tar.gz
bpf--release--0.1--patch-1.tar.gz
bpf--release--0.1--patch-2.tar.gz
[...]
bpf--release--0.1--patch-8.tar.gz

I unpacked these:

$ for f in *.tar.gz; do tar -xz < "$f" || echo >&2 "$f" failed; done

The last revision's tree apparently contains all previous revisions' commit information (author, date, message), so use that:

$ cp -a ↩
    bpf--release--0.1--patch-8/{arch}/bpf/bpf--devel/bpf--devel--0.0/info@hurdfr.org--hurdfr/patch-log ↩
    d-patch-log
$ cp -a ↩
    bpf--release--0.1--patch-8/{arch}/bpf/bpf--release/bpf--release--0.1/info@hurdfr.org--hurdfr/patch-log ↩
    r-patch-log

... and extract the information that we need:

$ base=bpf--devel--0.0-- && ↩
  for f in d-patch-log/*; do ↩
    grep < "$f" ^Creator: | head -n 1 ↩
      | { read j c && ↩
          echo "$c" | sed s%' <.*'%% ↩
            > "$base""$(basename "$f")".author_name && ↩
          echo "$c" | sed -e 's%.*<%%' -e 's%>.*%%' ↩
            > "$base""$(basename "$f")".author_email; } && ↩
    grep < "$f" ^Standard-date: | head -n 1 | { read j d && echo "$d" ↩
      > "$base""$(basename "$f")".author_date; } && ↩
    { grep < "$f" ^Summary: | head -n 1 | { read j m && echo "$m"; } && ↩
      echo && sed < "$f" '1,/^$/d'; } ↩
      > "$base""$(basename "$f")".log ↩
    || echo >&2 "$f" failed; ↩
  done
$ base=bpf--release--0.1-- && ↩
  for f in r-patch-log/*; [...]

(Of course, I could have used something more elaborate than shell scripting...)

Remove the GNU arch stuff that we don't need anymore:

$ find bpf--*/ -type d \( -name {arch} -o -name .arch-ids \) -print0 ↩
    | xargs -0 rm -r

The base-0 revisions are actually either empty (the devel one) or equivalent to the previous revision (the release one), so remove these:

$ rm -rf bpf--devel--0.0--base-0 bpf--release--0.1--base-0

Finally, import all the other ones:

$ mkdir g && ( cd g/ && git init )
$ for d in bpf--d*-? bpf--d*-?? bpf--r*; do ↩
    test -d "$d"/ || continue && ↩
    ( cd g/ && ↩
      rsync -a --delete --exclude=/.git ../"$d"/ ./ && ↩
      git add . && ↩
      GIT_AUTHOR_NAME="$(cat ../"$d".author_name)" ↩
        GIT_AUTHOR_EMAIL="$(cat ../"$d".author_email)" ↩
        GIT_AUTHOR_DATE="$(cat ../"$d".author_date)" ↩
        git commit -F ../"$d".log -a ); ↩
  done

Voilà!

Update 2009-06-25:

Half a day later, ?HurdFr published a git archimport-converted repository -- which was identical to my hand-crafted one (apart from having git-archimport-id: tags in the commit messages, and the first (empty) commit not being stripped off).