Dump github/gitlab/gitea repository data to a local directory and restore to gitea

[lunny]

Currently online migrating is possible but in fact, it depends on the internet network status what's a mess. This PR makes it possible to dump a repository on GitHub/GitLab/Gitea to a disk directory and then transfer it to another Gitea instance via the possible transfer method. And then restore the repository on the target Gitea instance.

i.e. Gitea repository itself in GitHub spent about 80 GB but transfer 80GB online is almost impossible. Then we can dump the repository to a host nearby Github's host and then compress it and transfer it to another host.

A new Gitea command has been added to do the things, you can use it as below:

./gitea dump-repo --repo_dir ./dumps --clone_addr https://github.com/go-xorm/builder.git --auth_username <token> --owner_name xorm --repo_name builder 

A dumped repository(go-gitea/test_repo) directory structure like this.

Another command is restore-repo added from this PR which could restore the repository to a Gitea instance from the dumped folder.

./gitea restore-repo --repo_dir ./dumps/xorm/builder --owner_name xorm --repo_name builder 

And this could be also used as a backup tool to backup repositories in Github/Gitlab/Gitea .

• Add a command gitea dump-repo
• Add a command gitea restore-repo

[6543]

@lunny one thing left: we should also save the git-service type and source url somewhere

[6543]

... to be able to migrate issue/pull ownership to existing users as we can do with the normal github/gitlab migration now

[codecov-commenter]

Codecov Report

Merging #12244 into master will increase coverage by 0.66%.
The diff coverage is 1.49%.

@@ Coverage Diff @@## master #12244 +/- ## ========================================== + Coverage 42.59% 43.25% +0.66%  ========================================== Files 671 645 -26 Lines 73635 71468 -2167 ========================================== - Hits 31365 30917 -448 + Misses 37184 35543 -1641 + Partials 5086 5008 -78 

Impacted Files	Coverage Δ
cmd/dump_repo.go	0.00% <0.00%> (ø)
modules/migrations/base/pullrequest.go	0.00% <ø> (ø)
modules/migrations/dump.go	0.00% <0.00%> (ø)
modules/structs/repo.go	54.54% <ø> (+4.54%)	⬆️
modules/migrations/migrate.go	22.47% <41.66%> (+0.91%)	⬆️
routers/api/v1/settings/settings.go	44.44% <0.00%> (-55.56%)	⬇️
modules/storage/local.go	0.00% <0.00%> (-38.10%)	⬇️
modules/queue/queue.go	24.39% <0.00%> (-7.87%)	⬇️
models/attachment.go	54.86% <0.00%> (-6.25%)	⬇️
modules/webhook/matrix.go	30.30% <0.00%> (-4.67%)	⬇️
... and 208 more

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[techknowlogick]

please resolve conflict

[techknowlogick]

CI fail is related:

level=warning msg="[runner] Can't run linter goanalysis_metalinter: S1008: failed prerequisites: [([email protected]/gitea/modules/cron, [email protected]/gitea/modules/cron): analysis skipped: errors in package: [/go/src/code.gitea.io/gitea/modules/cron/tasks_basic.go:12:2: could not import code.gitea.io/gitea/modules/migrations (/go/src/code.gitea.io/gitea/modules/migrations/dump.go:514:29: cannot use downloader (variable of type *RepositoryRestorer) as base.Downloader value in argument to DoMigrateRepository: wrong type for method GetAsset)]]" level=warning msg="[runner] Can't run linter unused: buildir: analysis skipped: errors in package: [/go/src/code.gitea.io/gitea/modules/migrations/dump.go:514:29: cannot use downloader (variable of type *RepositoryRestorer) as base.Downloader value in argument to DoMigrateRepository: wrong type for method GetAsset -: could not load export data: no export data for \"code.gitea.io/gitea/modules/migrations\"]" level=error msg="Running error: buildir: analysis skipped: errors in package: [/go/src/code.gitea.io/gitea/modules/migrations/dump.go:514:29: cannot use downloader (variable of type *RepositoryRestorer) as base.Downloader value in argument to DoMigrateRepository: wrong type for method GetAsset -: could not load export data: no export data for \"code.gitea.io/gitea/modules/migrations\"]" 

[6543]

I think we should stave CloneURL to yaml too
why not move Topics into a generell repo.yml ?
so the local "import" still has the right urls ...

[codecov-io]

Codecov Report

Merging #12244 (695d23e) into master (cf9d471) will decrease coverage by 0.29%.
The diff coverage is 3.25%.

@@ Coverage Diff @@## master #12244 +/- ## ========================================== - Coverage 42.36% 42.06% -0.30%  ========================================== Files 728 733 +5 Lines 78015 78666 +651 ========================================== + Hits 33049 33093 +44 - Misses 39540 40159 +619 + Partials 5426 5414 -12 

Impacted Files	Coverage Δ
cmd/dump_repo.go	0.00% <0.00%> (ø)
cmd/restore_repo.go	0.00% <0.00%> (ø)
models/admin.go	60.31% <0.00%> (-8.78%)	⬇️
models/task.go	34.95% <ø> (+0.04%)	⬆️
modules/migrations/base/downloader.go	17.51% <ø> (ø)
modules/migrations/base/pullrequest.go	0.00% <ø> (ø)
modules/migrations/dump.go	0.00% <0.00%> (ø)
modules/migrations/error.go	100.00% <ø> (ø)
modules/migrations/git.go	46.42% <ø> (+3.09%)	⬆️
modules/migrations/gitea_downloader.go	0.91% <0.00%> (+<0.01%)	⬆️
... and 29 more

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[6543]

@lunny "migrations/restore.go exported methods should have comment or be unexported"

[lunny]

@techknowlogick done.