1. Go to Mage Repository
2. Run command exemplified below:

For cards added since tagOrSha1 till head revision (you can replace HEAD with another tagOrSha1):
git log tagOrSha1..HEAD --diff-filter=A --name-status | sed -ne 's/^A[^u]Mage.Sets\/src\/mage\/sets\///p' | sort -u > added_cards.txt

for Windows: you need to replace ' by "" and remove -u in sort

Example for cards implemented from 0.8.7 till 0.9:
git log 9ac166abc92f70aebdbe34825880ff8f909465ed..HEAD --diff-filter=A --name-status | sed -ne "s/^A[^u]Mage.Sets\/src\/mage\/sets\///p" | sort > added_cards.txt
since 1.0.2-release:
git log 6b38cd5b18298b07962b969bfa2eb69c62839575..HEAD --diff-filter=A --name-status | sed -ne "s/^A[^u]Mage.Sets\/src\/mage\/sets\///p" | sort > added_cards.txt
since 1.0.3-release:

3. Copy added_cards.txt to trunk\Utils folder
4. Run script:
> perl extract_in_wiki_format.perl
5. Open added_cards_in_wiki_format.txt
6. Copy content to release notes