Document behavior of AWS {access,secret}_key in relation to credentials file...

Document behavior of AWS {access,secret}_key in relation to credentials file and profile lookup via AWS_PROFILE

website/source/docs/builders/amazon-chroot.html.markdown

@@ -58,11 +58,9 @@ can be configured for this builder.
 ### Required:
 
 * `access_key` (string) - The access key used to communicate with AWS.
-  If not specified, Packer will use the key from any [credentials](http://docs.aws.amazon.com/cli/latest/userguide/cli-chap-getting-started.html#cli-config-files) file
-  or fall back to environment variables `AWS_ACCESS_KEY_ID` or `AWS_ACCESS_KEY` (in that order), if set.
-  If the environmental variables aren't set and Packer is running on
-  an EC2 instance, Packer will check the instance metadata for IAM role
-  keys.
+  If not specified, Packer will search the standard [credentials](http://docs.aws.amazon.com/cli/latest/userguide/cli-chap-getting-started.html#cli-config-files) file using environment variable `AWS_PROFILE` as the profile name, will use the `[default]` entry,
+  or will fall back to environment variables `AWS_ACCESS_KEY_ID` or `AWS_ACCESS_KEY`. 
+  Finally, if Packer is running on an EC2 instance it will check the instance metadata for IAM role keys.
 
 * `ami_name` (string) - The name of the resulting AMI that will appear
   when managing AMIs in the AWS console or via APIs. This must be unique.
@@ -70,11 +68,7 @@ can be configured for this builder.
   [configuration templates](/docs/templates/configuration-templates.html) for more info)
 
 * `secret_key` (string) - The secret key used to communicate with AWS.
-  If not specified, Packer will use the secret from any [credentials](http://docs.aws.amazon.com/cli/latest/userguide/cli-chap-getting-started.html#cli-config-files) file
-  or fall back to environment variables `AWS_SECRET_ACCESS_KEY` or `AWS_SECRET_KEY` (in that order), if set.
-  If the environmental variables aren't set and Packer is running on
-  an EC2 instance, Packer will check the instance metadata for IAM role
-  keys.
+  Lookup behavior is as above for `access_key` except the variables are `AWS_SECRET_ACCESS_KEY` or `AWS_SECRET_KEY`.
 
 * `source_ami` (string) - The source AMI whose root volume will be copied
   and provisioned on the currently running instance. This must be an

website/source/docs/builders/amazon-ebs.html.markdown

@@ -38,8 +38,9 @@ can be configured for this builder.
 ### Required:
 
 * `access_key` (string) - The access key used to communicate with AWS.
-  If not specified, Packer will use the key from any [credentials](http://docs.aws.amazon.com/cli/latest/userguide/cli-chap-getting-started.html#cli-config-files) file
-  or fall back to environment variables `AWS_ACCESS_KEY_ID` or `AWS_ACCESS_KEY` (in that order), if set.
+  If not specified, Packer will search the standard [credentials](http://docs.aws.amazon.com/cli/latest/userguide/cli-chap-getting-started.html#cli-config-files) file using environment variable `AWS_PROFILE` as the profile name, will use the `[default]` entry, 
+  or will fall back to environment variables `AWS_ACCESS_KEY_ID` or `AWS_ACCESS_KEY`.
+  Finally, if Packer is running on an EC2 instance it will check the instance metadata for IAM role keys.
 
 * `ami_name` (string) - The name of the resulting AMI that will appear
   when managing AMIs in the AWS console or via APIs. This must be unique.
@@ -53,8 +54,7 @@ can be configured for this builder.
   to launch the EC2 instance to create the AMI.
 
 * `secret_key` (string) - The secret key used to communicate with AWS.
-  If not specified, Packer will use the secret from any [credentials](http://docs.aws.amazon.com/cli/latest/userguide/cli-chap-getting-started.html#cli-config-files) file
-  or fall back to environment variables `AWS_SECRET_ACCESS_KEY` or `AWS_SECRET_KEY` (in that order), if set.
+  Lookup behavior is as above for `access_key` except the variables are `AWS_SECRET_ACCESS_KEY` or `AWS_SECRET_KEY`
 
 * `source_ami` (string) - The initial AMI used as a base for the newly
   created machine.

website/source/docs/builders/amazon-instance.html.markdown

@@ -43,8 +43,9 @@ can be configured for this builder.
 ### Required:
 
 * `access_key` (string) - The access key used to communicate with AWS.
-  If not specified, Packer will use the key from any [credentials](http://docs.aws.amazon.com/cli/latest/userguide/cli-chap-getting-started.html#cli-config-files) file
-  or fall back to environment variables `AWS_ACCESS_KEY_ID` or `AWS_ACCESS_KEY` (in that order), if set.
+  If not specified, Packer will search the standard [credentials](http://docs.aws.amazon.com/cli/latest/userguide/cli-chap-getting-started.html#cli-config-files) file using environment variable `AWS_PROFILE` as the profile name, will use the `[default]` entry,
+  or will fall back to environment variables `AWS_ACCESS_KEY_ID` or `AWS_ACCESS_KEY`.
+  Finally, if Packer is running on an EC2 instance it will check the instance metadata for IAM role keys.
 
 * `account_id` (string) - Your AWS account ID. This is required for bundling
   the AMI. This is _not the same_ as the access key. You can find your
@@ -65,8 +66,8 @@ can be configured for this builder.
   This bucket will be created if it doesn't exist.
 
 * `secret_key` (string) - The secret key used to communicate with AWS.
-  If not specified, Packer will use the secret from any [credentials](http://docs.aws.amazon.com/cli/latest/userguide/cli-chap-getting-started.html#cli-config-files) file
-  or fall back to environment variables `AWS_SECRET_ACCESS_KEY` or `AWS_SECRET_KEY` (in that order), if set.
+  Lookup behavior is as above for `access_key` except the variables are `AWS_SECRET_ACCESS_KEY` or `AWS_SECRET_KEY`
+
 
 * `source_ami` (string) - The initial AMI used as a base for the newly
   created machine.

website/source/docs/builders/amazon.html.markdown

@@ -33,8 +33,8 @@ much easier to use and Amazon generally recommends EBS-backed images nowadays.
 
 ## Using an IAM Instance Profile
 
-If AWS keys are not specified in the template, a [credentials](http://docs.aws.amazon.com/cli/latest/userguide/cli-chap-getting-started.html#cli-config-files) file or through environment variables
-Packer will use credentials provided by the instance's IAM profile, if it has one.
+If AWS keys are not specified in the template, Packer will consult the [credentials](http://docs.aws.amazon.com/cli/latest/userguide/cli-chap-getting-started.html#cli-config-files) file, try the standard AWS environment variables, and then
+any IAM role credentials defined by the instance's metadata.
 
 The following policy document provides the minimal set permissions necessary for Packer to work: