Enhance result string for merge

[danghai]

Because we are going to implement the ordered mixture of merge arguments following multiple patch, the result string only stores True/False. In my opinion, result string should be enhanced by providing more detail information. Ex:

<Name of Patch1> : True
<Name of Patch2> : True
<Name of Patch3> : False

What do you think?

[veruu]

The result_string is meant to be an indicator of the command result - something like permanent storage of return code. There is a huge discussion in meta/6 if you want to follow the reasoning, but the short version is

• if the command didn't complete (eg. got an unexpected exception), there is no file with the result
• if the command completed unsuccessfully, there is a result file with false string
• if the command completed successfully, there is a result file with true string

The strings are shell commands at the same time, so the files are easy to process by machine. What patches were applied should be present in the report itself (report_string and file that's created if the command completes).