default-packages doesn't install last package in file on Mac and Raspbian 12

[MynockSpit]

The command for ensuring a trailing new line in the list of default packages doesn't work in Mac and Raspbian 12. Instead it silently does nothing. This means that if you fail to put a new line in the default-packages file manually, the last package is ignored.

Notes

Command in nvm.sh:

$ echo '---'; echo -e "one\ntwo" | sed -e '$a\'; echo '---'
---
one
two
---

As an example (and not a replacement!) this is what it would look like on Mac and Raspbian 12.

$ echo '---'; echo -e "one\ntwo" | sed -e $'$a\\\n\\'; echo '---'
---
one
two

---

I'm no expert by any means, but perhaps an alternative such as while IFS="" read -r p || [ -n "$p" ] would work more broadly, and also wouldn't require rewriting the file into tmp.

Operating systems and versions:

Mac OS 14.2.1 (23C71) / nvm 0.39.7
Raspbian 12 / nvm 0.39.7

[MynockSpit]

Update: After a little testing, it looks like the following command works on Raspi, but not on Mac.

Raspbian:

$ echo '---'; echo -e "one\ntwo" | sed -e '$a\\'; echo '---'
---
one
two

---

Mac:

$ echo '---'; echo -e "one\ntwo" | sed -e '$a\\'; echo '---'
---
sed: 1: "$a\\
": extra characters after \ at the end of a command
---

[ljharb]

ok, i can definitely reproduce this, but the test in db19450 should be preventing it.

I'd definitely prefer to avoid the tempfile if possible.