I am making an assumption `OutputMode.none` should _really_ mean
`OutputMode.failuresOnly`, that is, if we ever get a non-zero exit code,
we still want to know why. If I've somehow misunderstood that, LMK and
I'm happy to revert this PR or make adjustments.
This fixes the bug where if you were to do:
```sh
git clone https://github.com/myuser/fork-of-flutter
cd fork-of-flutter
./bin/flutter update-packages
```
You now get:
1. An actual error message, versus no output at all.
2. A warning that a common reason is not tracking a remote, with
instructions to fix it.
Closes https://github.com/flutter/flutter/issues/148569.
This pull request fixes#143803 by taking advantage of Dart's null-aware operators.
And unlike `switch` expressions ([9 PRs](https://github.com/flutter/flutter/pull/143634) and counting), the Flutter codebase is already fantastic when it comes to null-aware coding. After refactoring the entire repo, all the changes involving `?.` and `??` can fit into a single pull request.
Fixes https://github.com/flutter/flutter/issues/133093
When I introduced the new, more robust version file `//flutter/bin/cache/version.json` in https://github.com/flutter/flutter/pull/124558, I changed `class FlutterVersion` into an abstract interface, implemented by `_FlutterVersionFromGit` (which is essentially the previous behavior) and `_FlutterVersionFromFile`, which merely reads the data it would have computed via git from `//flutter/bin/cache/version.json`.
While doing this, I made `_FlutterVersionFromGit.ensureVersionFile()` to be a no-op, since I assumed this would not be necessary since we already had a version file in the cache. However, this method was what was previously responsible for ensuring `//flutter/version` existed on disk. This means that if, for whatever reason, the user had `//flutter/bin/cache/flutter.version.json` present but NOT `//flutter/version`, the tool would have never created that file, and they would hit the tool crash seen in https://github.com/flutter/flutter/issues/133093.
This fixes the tool by ensuring `//flutter/version` exists regardless of if we're hydrating `FlutterVersion` from `//flutter/bin/cache/flutter.version.json` or not.
Fixes https://github.com/flutter/flutter/issues/112833
Most of the actual changes here are in [packages/flutter_tools/lib/src/version.dart](https://github.com/flutter/flutter/pull/124558/files#diff-092e00109d9e1589fbc7c6de750e29a6ae512b2dd44e85d60028953561201605), while the rest is largely just addressing changes to the constructor of `FlutterVersion` which now has different dependencies.
This change makes `FlutterVersion` an interface with two concrete implementations:
1. `_FlutterVersionGit` which is mostly the previous implementation, and
2. `_FlutterVersionFromFile` which will read a new `.version.json` file from the root of the repo
The [`FlutterVersion` constructor](https://github.com/flutter/flutter/pull/124558/files#diff-092e00109d9e1589fbc7c6de750e29a6ae512b2dd44e85d60028953561201605R70) is now a factory that first checks if `.version.json` exists, and if so returns an instance of `_FlutterVersionFromGit` else it returns the fallback `_FlutterVersionGit` which will end up writing `.version.json` so that we don't need to re-calculate the version on the next invocation.
`.version.json` will be deleted in the bash/batch entrypoints any time we need to rebuild he tool (this will usually be because the user did `flutter upgrade` or `flutter channel`, or manually changed the commit with git).
## How we determine the channel name
Historically, we used the current branch's upstream to figure out the current channel name. I have no idea why. I traced it back to https://github.com/flutter/flutter/pull/446/files where @abarth implement this and I reviewed that PR and left no comment on it at the time.
I think this is confusing. You can be on a branch and it tells you that your channel is different. That seems weird.
This PR changes the logic to uses the current branch as the channel name.
## How we display channels
The main reason this PR exists is to add channel descriptions to the `flutter channel` list:
```
ianh@burmese:~/dev/flutter/packages/flutter_tools$ flutter channel
Flutter channels:
master (tip of tree, for contributors)
main (tip of tree, follows master channel)
beta (updated monthly, recommended for experienced users)
stable (updated quarterly, for new users and for production app releases)
* foo_bar
Currently not on an official channel.
ianh@burmese:~/dev/flutter/packages/flutter_tools$
```
## Other changes
I made a few other changes while I was at it:
* If you're not on an official channel, we used to imply `--show-all`, but now we don't, we just show the official channels plus yours. This avoids flooding the screen in the case the user is on a weird channel and just wants to know what channel they're on.
* I made the tool more consistent about how it handles unofficial branches. Now it's always `[user branch]`.
* I slightly adjusted how unknown versions are rendered so it's clearer the version is unknown rather than just having the word "Unknown" floating in the output without context.
* Simplified some of the code.
* Made some of the tests more strict (checking all output rather than just some aspects of it).
* Changed the MockFlutterVersion to implement the FlutterVersion API more strictly.
* I made sure we escape the output to `.metadata` to avoid potential injection bugs (previously we just inlined the version and channel name verbatim with no escaping, which is super sketchy).
* Tweaked the help text for the `downgrade` command to be clearer.
* Removed some misleading text in some error messages.
* Made the `.metadata` generator consistent with the template file.
* Removed some obsolete code to do with the `dev` branch.
## Reviewer notes
I'm worried that there are implications to some of these changes that I am not aware of, so please don't assume I know what I'm doing when reviewing this code. :-)
* Create a main alias for master channel.
To slowly migrate away from master branch in the flutter repository we
created a main branch that is mirroring master branch. This PR is also
adding a channel alias that will allow to use master/main interchangeably.
Bug: https://github.com/flutter/flutter/issues/95041
* Fix channel tests.
* Remove additional space.
