Add an alternate regex delimiter (cf. leaning toothpicks)

[mike-clark-8192]

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GitHub code search uses the traditional / character to indicate a regex search (/regex/). One of the problems with / is leaning toothpick syndrome. I propose GitHub introduce an additional, alternate, delimiter. To that end, I reviewed all ASCII punctuation characters in a number of feature dimensions, scored them, and sorted them by score.
If anyone has any questions, feel free to ask! Here's the data:

	GH Search	Search 1	Code	Data 2	Regex	Score 3
~	✔	◑ 4	✔	✔	✔	4.50
%	◑ 5	◑ 5	◑ 6	✔	✔	3.50
^	✔	◑ 7	◕ 8	✔	✗ 9	3.25
$	✔	✔	✗ 10	✔	✗ 9	3.00
!	◑ 75	◔ 7	◔ 7	✔	✔	3.00
`	◑ 1112	◕ 1112	◔ 6131211	◑ 11	✔	3.00
{}	✔	✔	◔	✗	◑ 14	2.75
&	◑ 7	◔ 7	◔ 7	◔ 15	✔	2.25
<	✗ 16	◔ 7	◔ 75	◕	✔	2.25
;	◔ 17	◔ 17	✗ 5	◑	✔	2.00
'	◔ 13	◔ 13	✗	◔ 13	✔	1.75
#	◔ 18	◔ 18	✗ 19	◔ 19	✔	1.75
+	◑ 75	◔ 720	✗ 6	✔	✗ 17	1.75
>	✗ 16	◔ 7	✗ 17	◑	✔	1.75
@	✗ 16	◔ 21	◔ 5	◔ 5	✔	1.75
,	◔ 5	◔ 5	✗	✗	✔	1.50
-	✗ 7	✗ 7	✗ 8	◑ 5	✔	1.50
=	✗ 16	◔ 7	✗ 17	✗ 17	✔	1.25
|	◑ 7	◔ 7	◔ 76	◔	✗ 17	1.25
"	✗ 16	✗ 1319	✗	✗	✔	1.00
*	✗ 16	✗ 6	✗ 822	✔	✗ 17	1.00
:	✗ 16	✗ 16	✗	✗	✔	1.00
?	✗ 5	◔ 20	◔ 17	◑	✗ 17	1.00
()	✗ 23	✗ 23	✗	◑	◔ 23	0.75
[	◔ 5	◔ 23	✗ 17	◔ 5	✗ 5	0.75
]	◔ 5	◔ 23	✗ 17	◔ 5	✗ 5	0.75
\	◔ 12	◔ 12	✗ 12	✗ 12	✗ 12	0.50
_	✗ 524	◔ 524	✗ 524	✗ 524	✗ 524	0.25
.	✗ 5	✗ 5	✗6	✗ 517	✗ 6	0.00
/	✗ 16	✗ 25	✗ 825	✗ 425	✗ 6	0.00

Footnotes

1. "Search" as a general, widely implemented concept ↩

2. JSON, YAML, INI, TOML, etc. ↩

3. ✔=1.0   ◕=0.75   ◑=0.5   ◔=0.25   ✗=0.0 ↩

4. "approximate", ≈ ≲ ≅ etc. ↩ ↩²

5. common punctuation ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸ ↩⁹ ↩¹⁰ ↩¹¹ ↩¹² ↩¹³ ↩¹⁴ ↩¹⁵ ↩¹⁶ ↩¹⁷ ↩¹⁸ ↩¹⁹ ↩²⁰ ↩²¹ ↩²² ↩²³ ↩²⁴ ↩²⁵ ↩²⁶

6. metacharacter ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸

7. Boolean logic ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸ ↩⁹ ↩¹⁰ ↩¹¹ ↩¹² ↩¹³ ↩¹⁴ ↩¹⁵ ↩¹⁶ ↩¹⁷ ↩¹⁸

8. arithmetic ↩ ↩² ↩³ ↩⁴

9. commonly used at start/end of regex ↩ ↩²

10. $var is just so common ↩

11. markdown ↩ ↩² ↩³ ↩⁴

12. escaping ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸

13. quoting ↩ ↩² ↩³ ↩⁴ ↩⁵

14. precedent as alternate regex delimiter with vim, perl, sed, etc., but is also a regex metachar ↩

15. YAML, HTML ↩

16. in use ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸ ↩⁹

17. separator ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸ ↩⁹ ↩¹⁰ ↩¹¹ ↩¹² ↩¹³

18. #tag #topic, etc. ↩ ↩²

19. comment character ↩ ↩² ↩³

20. aka "required" search term ↩ ↩²

21. @username ↩

22. pointers, splatting ↩

23. grouping ↩ ↩² ↩³ ↩⁴ ↩⁵

24. pseudo-letter ↩ ↩² ↩³ ↩⁴ ↩⁵

25. URLs, Paths ↩ ↩² ↩³