Created SC2049 (markdown)

SC2049.md

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+## =~ is for regex, but this looks like a glob. Use = instead.
+
+### Problematic code:
+
+```sh
+[[ $file =~ *.txt ]]
+```
+
+### Correct code:
+
+```sh
+[[ $file = *.txt ]]
+```
+
+### Rationale:
+
+You are using `=~` to match against a regex -- specifically a Extended Regular Expression (ERE) -- but the right-hand side looks more like a glob:
+
+* It may have a leading `*`, like in `*.txt`
+    * In a glob, this matches strings ending in `.txt`, like `readme.txt` but not `foo.sh`
+    * In an ERE, this matches a literal asterisk, followed by any character, and then `txt`, such as `*itxt` but not `test.txt`
+
+* It may be a single letter followed by a `*`, like in `s*`. 
+    * In a glob, this matches strings starting with `s`, such as `shell` and `set`.
+    * In an ERE, this matches zero or more `s`s, such as `dog` (because it does in fact contain zero or more `s`'s)
+
+Please ensure that the pattern is correct as an ERE, or switch to glob matching if that's what you intended.
+
+This is similar to [[SC2063]], where `grep "*foo*"` produces an equivalent warning.
+
+### Exceptions:
+
+If you are aware of the difference, you can [[ignore]] this message, but this warning is not emitted for the more probable EREs `\*.txt`, `\.txt$`, `^s` or `s+`, so it should rarely be necessary.
+
+### Related resources:
+
+* Help by adding links to BashFAQ, StackOverflow, man pages, POSIX, etc!