Shorthand for diff of git commit with its parent?

Aside from writing an alias or script, is there a shorter command for getting the diff for a particular commit?

git diff 15dc8^..15dc8

If you only give the single commit id git diff 15dc8, it diffs that commit against HEAD.

From stackoverflow Brian L

• Use git show $COMMIT. It'll show you the log message for the commit, and the diff of that particular commit.

  orip : Too bad it can't use difftool :(
  From mipadi

• If you know how far back, you can try something like:

  # Current branch vs. parent
  git diff HEAD^ HEAD
  
  # Current branch, diff between commits 2 and 3 times back
  git diff HEAD~3 HEAD~2
  

  Prior commits work something like this:

  # Parent of HEAD
  git show HEAD^1
  
  # Grandparent
  git show HEAD^2
  

  There are a lot of ways you can specify commits:

  # Great grandparent
  git show HEAD~3
  

  See this page for details.

  From Paul Vincent Craven

• Use git show COMMIT to get commit description and diff for a commit. If you want only diff, you can use git diff-tree -p COMMIT

  And if you read git-rev-parse(1) manpage carefully, you would notice the following fragment:

  Two other shorthands for naming a set that is formed by a commit and its parent commits exist. The r1^@ notation means all parents of r1. r1^! includes commit r1 but excludes all of its parents.

  This means that you can use 15dc8^! as a shorthand for 15dc8^..15dc8 anywhere in git where revisions are needed.

  orip : +1 Awesome, `r1^!` works with `git difftool`!!!
  From Jakub Narębski