Created SC2310 (markdown)

SC2310.md

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+## This function is invoked in an 'if' condition so set -e will be disabled. Invoke separately if failures should cause the script to exit.
+
+(This warning is optional and must be explicitly enabled)
+
+### Problematic code:
+
+```sh
+#!/bin/sh
+#shellcheck enable=check-set-e-suppressed
+
+set -e
+
+backup() {
+  cp *.txt /backup
+  rm *.txt            # Runs even if copy fails!
+}
+
+if backup
+then
+    echo "Backup successful"
+fi
+```
+
+### Correct code:
+
+```sh
+#!/bin/sh
+#shellcheck enable=check-set-e-suppressed
+
+set -e
+
+backup() {
+  cp *.txt /backup
+  rm *.txt
+}
+
+backup
+echo "Backup successful"
+```
+
+### Rationale:
+
+ShellCheck found a function used as a condition in a script where `set -e` is enabled. This means that the function will run without `set -e`, and will power through any errors.
+
+This applies to `if`, `while`, and `until` statements, commands negated with `!`, as well as the left-hand side of `||` and `&&`. It does matter how deeply the command is nested in such a structure.
+
+In the problematic example, the intent was that an error like `cp: error writing '/backup/important.txt': No space left on device` would cause the script to abort. Instead, since the function is invoked in an `if` statement, the script will proceed to delete all the files even though it failed to back them up.
+
+The fix is to call it outside of an `if` statement. There is no point in checking whether the command succeeded, since the script would abort if it didn't. You may also want to consider replacing `set -e` with explicit `|| exit` after every relevant command to avoid such surprises.
+
+### Exceptions:
+
+If you don't care that the function runs without `set -e`, you can disable this warning. 
+
+### Related resources:
+
+* BashFaq #105: [Why doesn't set -e (or set -o errexit, or trap ERR) do what I expected?](https://mywiki.wooledge.org/BashFAQ/105)