[Proposal] cli show migration enhancement

Issue type:

[ ] question [ ] bug report [X] feature request [ ] documentation issue

Database system/driver:

[X] cordova [X] mongodb [X] mssql [X] mysql / mariadb [X] oracle [X] postgres [X] cockroachdb [X] sqlite [X] sqljs [X] react-native [X] expo

TypeORM version:

[X ] latest [ ] @next [ ] 0.x.x (or put your version here)

Goals

To have greater confidence before applying / reverting migrations on a database.

Current state

Currently when running migrations from the cli useful information such as which migrations have been executed and the specific sql which would be run are displayed after the fact.

ts-node ./node_modules/typeorm/cli.js migration:run

Proposal

We propose to have functionality similar to https://docs.djangoproject.com/en/2.2/ref/django-admin/#django-admin-showmigrations which will allow the developer to receive the additional information before applying the changes.

e.g some options

# New command (which would list which has been applied or not and developer can determine which is going to be run / reverted)
ts-node ./node_modules/typeorm/cli.js migration:show

# additional flag
ts-node ./node_modules/typeorm/cli.js migration:run --plan
ts-node ./node_modules/typeorm/cli.js migration:revert --plan

Hoping to generate some discussion on the feature and we are happy to do the work and make the PR.

cc @Juddling

[pleerock]

Looks like this functionality can be useful, feel free to go with PR

[izayl]

why not add a flag to specific migration.

e.g

$ ts-node ./node_modules/typeorm/cli.js migration:run --target-migration
$ ts-node ./node_modules/typeorm/cli.js migration:revert --target-migration