cmp: helpful EOF messages

[mknos]

• It is easy to provide extra descriptive output when files differ at EOF, as done by GNU cmp
• Shell scripts running cmp would normally use the -s flag and check the exit code, i.e. the text description shouldn't be depended on for portability
• Also convert $chunk_size global to a constant because it doesn't vary

%dd if=/dev/urandom bs=512 count=1 of=rnd
%cp rnd rnd2
%echo >> rnd2
%touch empty
%perl cmp rnd rnd2 # test1: non-empty files, eof on arg1
cmp: EOF on rnd after byte 512, in line 6
%perl cmp rnd2 rnd # test2: non-empty files, eof on arg2
cmp: EOF on rnd after byte 512, in line 6
%perl cmp empty rnd # test3: arg1 empty
cmp: EOF on empty which is empty
%perl cmp rnd empty # test4: arg2 empty
cmp: EOF on empty which is empty

[coveralls]

Pull Request Test Coverage Report for Build 11439366106

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.7%) to 73.069%

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Totals
Change from base Build 11418850560:	-0.7%
Covered Lines:	350
Relevant Lines:	479

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💛 - Coveralls

[briandfoy]

changes: better messages when files differ at end of file