diff3: allow diff3 ed scripts to generate deletions

[thj]

Summary

diff3 with the -e (ed script flag) can generate line deletions, add support for
deletions and add a test case to exercise this behaviour. This functionality
was unearthed through comparison of bsd diff3 and gnu diff3 output.

[pstef]

usr.bin/diff3/diff3.c

142

I would use bool. It's a minor nit, but I think this code is unclear as it is.

527

The value of the boolean expression is used only once, so maybe it would be better to evaluate it directly in the function call?
Otherwise I would change the type of delete and move it to the if block - it doesn't seem to be used anywhere else.

[thj]

usr.bin/diff3/diff3.c

527

I'll convert it to bool, I think having a variable helps make the code a little clearer here.

When -A and -m output modes come in they use the value of delete and I think consistency between the three output modes is a good idea.

[thj]

• Make delete bool

[thj]

• Only end ed input stream if we aren't issuing a delete

[thj]

• pass bool into prange in change