Add 6th ADR about shutting down our optparse-applicative fork

docs/ADR-6-Using-optparse-applicative-main-repository.md

@@ -0,0 +1,64 @@
+# Status
+
+📜 Proposed 2024-09-19
+
+# Context
+
+In 2021, we (the API and CLI team) wanted to improve the pretty printing of `optparse-applicative`,
+so that it aligns most flags vertically. E.g. we wanted this behavior:
+
+```
+Usage: cardano-cli transaction build-raw  
+            [ --byron-era
+            | --shelley-era
+            | --allegra-era
+            | --mary-era
+            | --alonzo-era
+            ]
+            ( --tx-in TX-IN
+              [ --tx-in-script-file FILE
+                [ (--tx-in-datum-file FILE | --tx-in-datum-value JSON VALUE)
+                  ( --tx-in-redeemer-file FILE
+                  | --tx-in-redeemer-value JSON VALUE
+                  )
+                  --tx-in-execution-units (INT, INT)
+                ]
+              ]
+            )
+            [--tx-in-collateral TX-IN]
+```
+
+instead of the default - less readable - behavior:
+
+```
+Usage: cardano-cli transaction build-raw [--byron-era | --shelley-era |
+                                           --allegra-era | --mary-era |
+                                           --alonzo-era] (--tx-in TX-IN
+                                         [--tx-in-script-file FILE
+                                           [
+                                             (--tx-in-datum-file FILE |
+                                               --tx-in-datum-value JSON VALUE)
+                                             (--tx-in-redeemer-file FILE |
+                                               --tx-in-redeemer-value JSON VALUE)
+                                             --tx-in-execution-units (INT, INT)]])
+                                         [--tx-in-collateral TX-IN]
+```
+
+Sadly the [PR we proposed](https://github.com/pcapriotti/optparse-applicative/pull/428#issuecomment-1559041183) to do that was never merged by the maintainer. Which is why we did our own fork: [input-output-hk/optparse-applicative](https://github.com/input-output-hk/optparse-applicative) and depended on this fork in [cardano-cli](https://github.com/IntersectMBO/cardano-cli/blob/ca494098df110dfcc23f14ef6635ec1b062baddf/cardano-cli/cardano-cli.cabal#L245).
+
+However, since 2021, `optparse-applicative`'s main repository [continued to evolve](https://github.com/pcapriotti/optparse-applicative/tags) and so our fork became out of date, adding to maintenance burden if we wanted to keep up.
+
+# Decision
+
+We want to get rid of our fork of `optparse-applicative`. Luckily, ideas from our initial PR were integrated into `optparse-applicative`'s main repo in 2023 (as mentioned [here](https://github.com/pcapriotti/optparse-applicative/pull/428#issuecomment-1559041183)), so we can now get better looking formatting of `--help` files nearly out of the box.
+
+We want to do a PR to `optparse-applicative` with the tweak we need. This time it is going to be a way smaller change than our PR from 2021 and so we are hopeful it will be accepted.
+
+# Consequences
+
+We have `cardano-cli` depend on [pcapriotti/optparse-applicative](https://github.com/pcapriotti/optparse-applicative) instead of [input-output-hk/optparse-applicative](https://github.com/input-output-hk/optparse-applicative), when our PR to `optparse-applicative` is merged and released.
+
+# References
+
+* [Our 2021 PR](https://github.com/pcapriotti/optparse-applicative/pull/428) to `optparse-applicative`'s main repo.
+* [Our fork](https://github.com/input-output-hk/optparse-applicative) of optparse-applicative.

docs/Architecture-Decision-Records.md

@@ -3,6 +3,7 @@
 * ✅ [[ADR-1 Default eras for CLI commands]]
 * ✅ [[ADR-2 Module structure for generators]]
 * 📜 [[ADR-3 Dependencies version constraints in cabal file]]
+* 📜 [[ADR-6 Using optparse-applicative main repository]]
 
 ## Legend