If grep is set to search only specific files (–include=a.txt), then grep does
not print a match even if there is one. First, main correctly adds the include
pattern with EXCLUDE_INCLUDE flag set (grep.c:2136-2140). When the files are
chosen for the search, files that are supposed to be included are actually
excluded because the return value of exclude_file_name is unnecessarily negated
(grep.c:2267-2269). The negation is unnecessary because the function
exclude_file_name is incorrectly assumed to treat excludes and includes the
same. However, the behavior changes if the EXCLUDE_INCLUDE flag is present
(lib/exclude.c:410, lib/exclude.c:359). 

Examples of Correct Fixes: 
1) Remove negation such that included_patterns are not excluded during
classification. 

2) Do not set EXCLUDE_INCLUDE flag for included_patterns which effectively
negates the faulty condition. 

Example of Incorrect Fix: 
Independent of whether a file matches the included_pattern, never exclude
(Regression because it doesn’t skip files that are *not* in the
included_patterns).
