Related T2026#37637

Related T2026#37637

Use case:

```
for r in $(python3 bin/list_repos.py --user SocialGouv); do
    python3 -m swh.loader.git.loader --origin-url $r
done
```

(oops)

this change make the export of a swh-storage containining the linux kernel
doable on ordinary laptop

for development use only

in particular, it now supports both running on the current git working
directory (the default) and specifying a list of git working directories to
analyze one after the other

to avoid stopping prematurely on out-of-order commits

to avoid stopping prematurely on out-of-order commits

specifically here the one from origin and origin_visit

Related D834

Related D831

Related D831

The last range is possibly quite smaller