Set a project environment variable

## Usage

`circleci envvar set <name> <value> [flags]`

## Arguments

`<name>` is the name of the environment variable to create or
update. `<value>` is the value to store; it is never retrievable
after being set and is masked in all subsequent list output.

## Flags

| Flag               | Description                                             |
| ------------------ | ------------------------------------------------------- |
| `--project string` | Project slug (e.g. gh/org/repo); defaults to git remote |

Global flags: `-c, --config`, `--debug`, `--no-color`, `-q, --quiet` — see `circleci --help`.

## Examples

- Set an env var for the current project: 
  `circleci envvar set MY_SECRET s3cr3t`
- Set an env var for a specific project: 
  `circleci envvar set MY_SECRET s3cr3t --project gh/myorg/myrepo`
- Read a value from a file: 
  `circleci envvar set MY_SECRET "$(cat secret.txt)"`

## Details

Create or update an environment variable for a CircleCI project.

If the variable already exists it will be overwritten. The value
is never retrievable after being set — CircleCI masks it in all
subsequent list responses.

