Metadata does not contain full path to input and output files

[juneb]

aws-encryption-sdk-cli 1.0.2.7
Windows 10.0.14393.1884
PowerShell 5.0.14393.1884
Related to: #65

The README and AWS Encryption SDK docs say that the CLI metadata contains the full path to the input and output files. This might be a misunderstanding of "full path."

When my working directory is: C:\test and my input file is C:\test\secret.txt, I expect the full path to my input file to be C:\test\secret.txt.

PS C:\test> (dir .\secret.txt).FullName
C:\test\secret.txt

Instead, the value of the input node in the metadata is: secret.txt

PS C:\test> $json | fl

header : @{algorithm=AES_256_GCM_IV12_TAG16_HKDF_SHA384_ECDSA_P384; content_type=2;
         encrypted_data_keys=System.Object[]; encryption_context=; frame_length=4096; header_iv_length=12;
         message_id=cWFfuKH2c0slnN0RZ9intA==; type=128; version=1.0}
input  : secret.txt
mode   : encrypt
output : .\secret.txt.encrypted

[mattsb42-aws]

Hmm, I thought checked this...apparently not. We'll want to make sure this is covered by tests before applying, but for reference while it's fresh in my head, the fix for this will be to update source file[1] and destination file[2] open calls to wrap the filename in os.path.abspath (we want abspath, not realpath so it displays as the file the caller specified rather than displaying the actual file following any symlinks).

[1] https://github.com/awslabs/aws-encryption-sdk-cli/blob/master/src/aws_encryption_sdk_cli/internal/io_handling.py#L332
[2] https://github.com/awslabs/aws-encryption-sdk-cli/blob/master/src/aws_encryption_sdk_cli/internal/io_handling.py#L257