How to get Git diff of the first commit?

Question

I created a repo, created a file inside it, put some content in the file, and committed the file. Now, I'd like to see a diff of that commit, which should ideally show the file that was added and the lines that were added to it.

However, git diff HEAD^ HEAD returns fatal: ambiguous argument 'HEAD^': unknown revision or path not in the working tree., probably because this was the first commit to the repo.

How can this be resolved? Is there still a way to view a diff of the files that were added in the first commit?

git show can work. But the first diff is always from null to the whole content. — ElpieKay
– ElpieKay, Commented Nov 30, 2016 at 8:50
@ElpieKay That works, but that also includes the commit summary. Possible to have it print only the diff without the commit summary If I do git show <file>? — Ali
– Ali, Commented Nov 30, 2016 at 8:54
git show <commit> --pretty=%% | sed 1,2d. %% could be any placeholder which outputs only one line, e.g. %h, %t. — ElpieKay
– ElpieKay, Commented Dec 1, 2016 at 12:40

Lara Bailey · Accepted Answer · 2016-11-30 09:03:28Z

158

You can do:

git diff 4b825dc642cb6eb9a060e54bf8d69288fbee4904 HEAD

4b825dc642cb6eb9a060e54bf8d69288fbee4904 is the id of the "empty tree" in Git and it's always available in every repository.

answered Nov 30, 2016 at 9:03

Lara Bailey

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11 Comments

gzh Over a year ago

@CharlesBaley, Cool, Where do you get this sha-1 code?

Lara Bailey Over a year ago

The id of the empty tree won't change while git continues to use sha1. You can use $(printf '' | git hash-object -t tree --stdin) for better readability.

Lara Bailey Over a year ago

@gzh: I remember common sha1s.

Daniel Waltrip Over a year ago

This is hilarious to me. Why not add a named flag for this? Something like git diff --empty-tree head. Similar to how we have --root for interactive rebase.

larsks Over a year ago

@DanielWaltrip maybe this is new, but git diff-tree now has a --root option that does exactly what you were asking about.

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Corey · Accepted Answer · 2022-09-20 22:54:27Z

11

Now that Git has experimental support for SHA256 and a transition plan for migrating the hash function from SHA1 to SHA256, you can no longer rely on a hash constant for the empty tree. Instead, it's best to dynamically retrieve it based on whatever hash function your repository is using:

git diff $(git hash-object -t tree /dev/null)

answered Sep 20, 2022 at 22:54

Corey

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Aya Salama · Accepted Answer · 2020-04-07 16:35:30Z

1

you can try:

git show <first-commit-sha>

or if you only have 1 commit you can simply use:

git show HEAD

answered Apr 7, 2020 at 16:35

Aya Salama

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1 Comment

Yasushi Shoji Over a year ago

It doesn't show the diff.

tfe · Accepted Answer · 2018-03-12 13:59:28Z

0

Maybe try with:

git log -p -n 1

answered Mar 12, 2018 at 13:59

tfe

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1 Comment

ErikE Over a year ago

This doesn't show the first commit. It shows the most recent one. It's not an answer to the given question.

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