ecs-cli configure --cluster short-name trashes its config file when you shorten the name of the cluster

[markriggins]

On OSX, if you build from the latest master 8c73f54, the ecs-cli configure command trashes its own config file if you shorten the name of the cluster.

To reproduce,

1. build from source on OSX

$ cd $GOPATH/github.com
$ mkdir aws
$ git clone [email protected]:aws/amazon-ecs-cli.git
$ cd amazon-ecs-cli
$ make build

2. create a valid config file with a long cluster name

$ mkdir -p home/.ecs
$ echo '[ecs]' > home/.ecs/config
$ HOME=$PWD/home bin/local/ecs-cli configure --cluster a-really-long-long-long-name
INFO[0000] Saved ECS CLI configuration for cluster (a-really-long-long-long-name) 
$ cat home/.ecs/config
[ecs]
cluster                     = a-really-long-long-long-name
aws_profile                 = 
region                      = 
aws_access_key_id           = 
aws_secret_access_key       = 
compose-project-name-prefix = ecscompose-
compose-service-name-prefix = ecscompose-service-
cfn-stack-name-prefix       = amazon-ecs-cli-setup-

Then update it with a shorter cluster name

$ HOME=$PWD/home bin/local/ecs-cli configure --cluster short-name
$ cat home/.ecs/config
[ecs]
cluster                     = short-name
aws_profile                 = 
region                      = 
aws_access_key_id           = 
aws_secret_access_key       = 
compose-project-name-prefix = ecscompose-
compose-service-name-prefix = ecscompose-service-
cfn-stack-name-prefix       = amazon-ecs-cli-setup-

n-ecs-cli-setup-

Notice the trash at the end of the config file. This happens because the file was opened and written to, but never truncated, so any extra stuff at the end of the file will remain as trash.

[markriggins]

Fixed in https://github.com/markriggins/amazon-ecs-cli/releases/tag/v0.4.4-with--cluster-flag