grep: correct handling of matching lines without line ending (issue3050)

Matching lines without trailing '\n' was missing the last character.

That seems to have been an unintended side effect of 261a9f47b44b.
The test in dac14cc9711e documents the bad behaviour.

mercurial/commands.py

@@ -2660,7 +2660,7 b' def grep(ui, repo, pattern, *pats, **opt'
             mstart, mend = match.span()
             linenum += body.count('\n', begin, mstart) + 1
             lstart = body.rfind('\n', begin, mstart) + 1 or begin
-            begin = body.find('\n', mend) + 1 or len(body)
+            begin = body.find('\n', mend) + 1 or len(body) + 1
             lend = begin - 1
             yield linenum, mstart - lstart, mend - lstart, body[lstart:lend]
 

tests/test-grep.t

@@ -106,12 +106,8 b' match in last "line" without newline'
   $ python -c 'fp = open("noeol", "wb"); fp.write("no infinite loop"); fp.close();'
   $ hg ci -Amnoeol
   adding noeol
-
-last character omitted in output to avoid infinite loop
-
   $ hg grep loop
-  noeol:4:no infinite loo
-
+  noeol:4:no infinite loop
 
   $ cd ..