handle spaces in filenames in file-list

[GochoMugo]

A filename with a space within, for example "spaced filename.txt" (contains a tab character in the filename),
and a hash digest, for example, "12345", would be recorded in the
file-list as:

spaced    filename.txt    12345

The current parser would determine that the <filename> is "spaced"
and the <sha> is "filename.txt". While this would not halt the
process, it would make the diffs-generation assume that the file has
been changed, which is incorrect.

We need to fix this bug:

Approach A:

An approach would be to quote the filename in the file-list. For example,

"spaced    filename.txt"    12345

But how to handle the " character in the filename? For example,

"comma\\"filename.txt"    12345

Approach B:

We could change the format, from <filename> <hash> to <hash> <filename>.
This is quite easier to implement. We are sure the <hash> can not contain
a space/tab character.

How to handle new input, with embedded space characters, being added to the
format.