Squash suggests non-multi-line long commit instead of title

Summary

According to our docs, we should suggest the first multi-line commit or the MR title as the squash message, however long commit messages (>100 characters) are considered multi-line because they are truncated after the title.

Reported by Starter customer with 350 seats in ZD (internal only).

Steps to reproduce

1. On a new branch, create a long commit message (> 100 characters)
2. Create a new MR, enabling the squash commits option
3. Notice that the suggested title is the long commit message instead of the MR title

Example Project

In cat/repro-squash-long-commits!1 (merged) the suggested squash message was the second, long, single-line commit message (see 0e7fbce3)

What is the current bug behavior?

The long, single-line commit is suggested as the squash commit message instead of the MR title.

What is the expected correct behavior?

The MR title should be suggested instead.

Possible fixes

Either the default squash message implementation could be updated to account for long commit messages or this might be considered expected, and would result in only a documentation change, but unsure about the inconsistency.