I ran into this situation few days ago, so I created a bash script, which will first query all email folders and then creates package.xml and retrieves all EmailTemplates using that package.xml.
This is assuming you are on a unix box and jq is installed.
1) Prepare a file named DownloadAllEmailTemplates.sh with below content:
rm -f temp.txt
rm -f ...
The EmailTemplate metadata type does not support wildcard retrieval - in package.xml or using the CLI. You need to specify each individual EmailTemplate you want to retrieve. E.g. sfdx force:source:retrieve -m EmailTemplate won't work, but sfdx force:source:retrieve -m EmailTemplate:folder/MyEmailTemplate should .
There seems to be something a bit funky about date comparison, and possibly short circuit evaluation, when you put that formula into the subject - (works fine in body of email).
If you just put in
IF( DAY(relatedTo.date_field_1__c) >
DAY(relatedTo.date_field_2__c), 'good', 'bad')
It gives error -
The value 'null' is not valid for operator '>'.
You can't really do what you'd want with typical email templates as they can only really display static images that you paste in or references to files that already exist. Since, in this case, the records/files will be created moments before (or be the trigger), it'll need to be able to dynamically pull them when the alert goes out. I can see one of two ...