This is functionally equivalent to the previous version (except for one
error case), but uses the new interface. I think the code is simpler
overall because it removes the line tracking.
This is a line-oriented parallel to io.ReaderAt, meant for text applies.
While the mapping isn't quite as clean as in the binary case, a text
apply still reads a fixed chunk of lines starting at a specific line
number and modifies them. This also allows a consistent interface for
strict and fuzzy applies.
The implementation wraps an io.ReaderAt and reads data in chunks,
indexing line boundaries as it goes. This is probably not the most
efficient way to implement this interface, but it works and allows file
application to take a consistent interface.
When applying, we need to copy all data after the last fragment line.
This function provides a way to get back the possibly-buffered io.Reader
that backs the LineReader.
LineReader is a wrapper around StringReader that counts line numbers.
This is not currently used by the parser, but will be used by the apply
functions.
Billy Keyes