Add the ability to apply missing (out-of-order) migrations

[mfridman]

Closes #249 #233 #262 #279 #172 and probably a bunch of other issues.

At a high, the library adds functional options to support applying missing or out-of-order migrations and the pre-built binary will have a new flag: -allow-missing=true or -out-of-order=true .. not sure which name folks like better? (suggestions welcome)

goose.Up(
	db, 
	migrationsDir, 
	goose.WithAllowMissing(), // <- apply missing migrations
)

Note. There was an existing bug reported previously, described in detail here #279. In this PR goose will detect "pending" migrations and return and error unless you enable the flags (CLI) or options (library) mentioned earlier. This should have always been the behaviour, but alas this might be a breaking change to some.

Those that follow hybrid-versioning should not have pending migrations and thus will not be affected.

• Add a dry-run options that display what migrations will be applied without applying them. This will be a separate feature.
• Add tests for down out-of-order migrations. Need to decide how to handle them, i.e., what order do you migrate down in? Probably based on the applied order instead of the version_id order.

Down migrations are applied in the reverse order they were applied. So up: 1, 4, 2, 3, 5 means down will be the reverse: 5, 3, 2, 4, 1.

[mfridman]

I keep flip flopping on the name, I've narrowed it down to:

• out-of-order
• allow-missing

[mfridman]

Going with "allow-missing" terminology, which is analogous to "out-of-order"

[mfridman]

One behaviour I don't like is that running Status displays migrations in the file order, instead of the applied database order. Which looks odd now that out-of-order migrations are supported.

This was always the default in goose .. but I think this should list migrations based on time applied instead of the file order. 🤔

Here I didn't apply migration 6 and 8. And the current Status returns:

2021/10/16 16:45:47 OK    00001_a.sql
2021/10/16 16:45:47 OK    00002_b.sql
2021/10/16 16:45:47 OK    00003_c.sql
2021/10/16 16:45:47 OK    00004_d.sql
2021/10/16 16:45:47 OK    00005_e.sql
2021/10/16 16:45:47 OK    00007_g.sql
2021/10/16 16:45:47     Applied At                  Migration
2021/10/16 16:45:47     =======================================
2021/10/16 16:45:47     Sat Oct 16 20:45:47 2021 -- 00001_a.sql
2021/10/16 16:45:47     Sat Oct 16 20:45:47 2021 -- 00002_b.sql
2021/10/16 16:45:47     Sat Oct 16 20:45:47 2021 -- 00003_c.sql
2021/10/16 16:45:47     Sat Oct 16 20:45:47 2021 -- 00004_d.sql
2021/10/16 16:45:47     Sat Oct 16 20:45:47 2021 -- 00005_e.sql
2021/10/16 16:45:47     Pending                  -- 00006_f.sql
2021/10/16 16:45:47     Sat Oct 16 20:45:47 2021 -- 00007_g.sql
2021/10/16 16:45:47     Pending                  -- 00008_h.sql

But then I ran Up allowing out-of-order migrations and then ran Status:

2021/10/16 16:45:52 OK    00006_f.sql
2021/10/16 16:45:52 OK    00008_h.sql
2021/10/16 16:45:52 goose: no migrations to run. current version: 8
2021/10/16 16:45:52     Applied At                  Migration
2021/10/16 16:45:52     =======================================
2021/10/16 16:45:52     Sat Oct 16 20:45:47 2021 -- 00001_a.sql
2021/10/16 16:45:52     Sat Oct 16 20:45:47 2021 -- 00002_b.sql
2021/10/16 16:45:52     Sat Oct 16 20:45:47 2021 -- 00003_c.sql
2021/10/16 16:45:52     Sat Oct 16 20:45:47 2021 -- 00004_d.sql
2021/10/16 16:45:52     Sat Oct 16 20:45:47 2021 -- 00005_e.sql
2021/10/16 16:45:52     Sat Oct 16 20:45:52 2021 -- 00006_f.sql <----- applied 5s after 
2021/10/16 16:45:52     Sat Oct 16 20:45:47 2021 -- 00007_g.sql
2021/10/16 16:45:52     Sat Oct 16 20:45:52 2021 -- 00008_h.sql <----- applied 5s after 

[mfridman]

Missing migrations now raise an error when attempting to apply migrations.

2021/10/24 11:00:38 OK    00001_a.sql
2021/10/24 11:00:38 OK    00002_b.sql
2021/10/24 11:00:38 OK    00003_c.sql
2021/10/24 11:00:38 OK    00004_d.sql
2021/10/24 11:00:38 OK    00005_e.sql
2021/10/24 11:00:38 OK    00007_g.sql
error: found 1 missing migrations:
        version 6: testdata/postgres/migrations/00006_f.sql