grep: implement -A context option

[mknos]

• Show non-matching context lines after a matching line
• A new match may occur within the context lines being displayed; this resets the context counter unless the match limit (-m value) was already reached
• Display a line of "--" to indicate the end of the context block
• If -A is used with -n, follow line number with '-' instead of ':' to indicate context lines
• When -A is used with -m, terminate the search at the end of the context and not the exact line triggering match limit

%perl grep -n -A 8 perl ar # test1: context bleeds into the line8 match
1:#!/usr/bin/perl
2-
3-=begin metadata
4-
5-Name: ar
6-Description: create and maintain library archives
7-Author: dkulp
8:License: perl
9-
10-=end metadata
11-
12-=cut
13-
14-use strict;
15-
16-use POSIX qw(strftime);
--
%perl grep -n -A 8 -m 1 perl ar # test2: line8 match doesn't count due to -m1 limit
1:#!/usr/bin/perl
2-
3-=begin metadata
4-
5-Name: ar
6-Description: create and maintain library archives 
7-Author: dkulp
8:License: perl
9-
--
%perl grep -A 4 perl ar # test3: no -n
#!/usr/bin/perl

=begin metadata

Name: ar
--
License: perl

=end metadata

=cut
--

[coveralls]

Pull Request Test Coverage Report for Build 11820740906

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%

---

Totals
Change from base Build 11816683101:	-0.7%
Covered Lines:	350
Relevant Lines:	479

---

💛 - Coveralls

[briandfoy]

changes: implement -A for context after a match