At the moment, we need only to read three lines, but now the value is
easy to adjust as needed. I've only seen the Git implementation read two
lines ahead so far, but it has the whole input in memory and may read
more in other places.
Call Next() to advance the parser state until it returns a non-nil
error, then check if the error is io.EOF. This makes EOF handling easier
and also means that Line() and PeekLine() can be called multiple times
without changing state.
The next step is to update parse functions to return an internal marker
error if they are called on an invalid line. This should improve
correctness and remove the duplication of testing a condition and then
calling a parse function, which checks the same condition.
In certain cases, the error is generated from the peeked next line or a
line that was read in the past. The delta flag corrects for this,
producing accurate error messages.
This avoids including the newline character as part of the name when it
is the last name on a line. Also split out functions for quoted and
unquoted names to clarify the logic.
The parsed OIDs are usually prefixes, not full hashes, so rename the
fields appropriately. Also note that values that are too long to be
valid OIDs are still accepted by the library.
Billy Keyes