This re-applies the fix in 5857 to make credentials.json writes concurrency safe.
The original fix used `path.Dir` instead of `filepath.Dir` - which led to not placing the temp file in the same folder (and drive) as the renamed file target. This led to errors on Windows environments where the working directory was on a different drive than the `~/.pulumi` directory. The change to use `filepath.Dir` instead ensures that even on Windows, the true directory containing the credentials file is used for the temp file as well.
Fixes#3877.
Running `pulumi` operations in parallel could occasionally result in truncating the `~/.pulumi/credentials.json` file and reading that truncated file from another process before the content could be written.
Instead, use `os.Rename` to atomically replace the file contents.
Concurrent `pulumi` operations could still compete for who gets to write the file first, and could lead to surprising results in some extreme cases. But we should not see the corrupted file contents any longer.
Fixes#3877.
The PULUMI_BACKEND_URL env var allows specifying the backend to use instead of deferring to the project or the ~/.pulumi/credentials.json file to decide on the "current" backend. This allows for using Pulumi without a dependence on this piece of global filesystem state, so that each `pulumi` invocation can control the exact backend it want's to operate on, without having to do stateful `pulumi login`/`pulumi logout` operations.
This is especially useful for automation scenarios like Automation API generally (and effectively solves https://github.com/pulumi/pulumi/issues/5591), or https://github.com/pulumi/pulumi-kubernetes-operator/issues/83 specifically.
This also makes things like efe7a599e6/dist/actions/entrypoint.sh (L10) less necessary, and possible to accomplish for any containerized `pulumi` execution without the need for this logic to be embedded in bash scripts wrapping the CLI.
* Make `async:true` the default for `invoke` calls (#3750)
* Switch away from native grpc impl. (#3728)
* Remove usage of the 'deasync' library from @pulumi/pulumi. (#3752)
* Only retry as long as we get unavailable back. Anything else continues. (#3769)
* Handle all errors for now. (#3781)
* Do not assume --yes was present when using pulumi in non-interactive mode (#3793)
* Upgrade all paths for sdk and pkg to v2
* Backport C# invoke classes and other recent gen changes (#4288)
Adjust C# generation
* Replace IDeployment with a sealed class (#4318)
Replace IDeployment with a sealed class
* .NET: default to args subtype rather than Args.Empty (#4320)
* Adding system namespace for Dotnet code gen
This is required for using Obsolute attributes for deprecations
```
Iam/InstanceProfile.cs(142,10): error CS0246: The type or namespace name 'ObsoleteAttribute' could not be found (are you missing a using directive or an assembly reference?) [/Users/stack72/code/go/src/github.com/pulumi/pulumi-aws/sdk/dotnet/Pulumi.Aws.csproj]
Iam/InstanceProfile.cs(142,10): error CS0246: The type or namespace name 'Obsolete' could not be found (are you missing a using directive or an assembly reference?) [/Users/stack72/code/go/src/github.com/pulumi/pulumi-aws/sdk/dotnet/Pulumi.Aws.csproj]
```
* Fix the nullability of config type properties in C# codegen (#4379)
