How to reference the initial commit?

Question

I've got a script that needs to reference the initial commit in a repository. git has the special reference HEAD, but doesn't have the corresponding TAIL. I cannot find anything in git help rev-parse that would seem to help me.

Here's what I'd like to do:

git show TAIL

Here's one option I have:

git show `git log --reverse | if read a commit ; then echo $commit ; fi`

That's pretty hacky and depends on the output of git log not changing.

Right now I just tag the initial commit and use that as my refspec. However, I'd like to release a general tool, so that's not a great option.

papanito · Accepted Answer · 2019-11-20 14:14:18Z

192

Do not use git-log for scripting: use either git-rev-list, or git-log with specified custom format (--format=*<sth>* option).

There is additional problem with your question: there can exist more than one such TAIL root commit (parentless commit) in a repository (even if we discount disconnected branches, such as 'html', 'man' and 'todo' in git.git repository). This is usually result of joining separate projects in one, or using subtree merge of separately developed subproject.

For example git repository has 6 root commits: git-gui, gitk (subtree-merged), gitweb (merged in, no longer developed separately), git mail tools (merged very early in project history), and p4-fast-export (perhaps accidental). That is not counting roots of 'html and 'man' branches, "convenience" branches which contains pre-generated documentation, and 'todo' branch with TODO list and scripts.

If you have git 1.7.4.2 or newer, you can use the --max-parents option:

$ git rev-list --max-parents=0 HEAD

Otherwise, you can get list of all parentless (root) commits accessible from current branch using:

$ git rev-list --parents HEAD | egrep "^[a-f0-9]{40}$"

edited Nov 20, 2019 at 14:14

papanito

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answered Jun 17, 2009 at 14:51

Jakub Narębski

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3 Comments

jbranchaud Over a year ago

For me, the git rev-list HEAD | tail -n 1 and git rev-list --max-parents=0 HEAD are not returning the same hash value for me. The one using the --max-parents=0 is in fact getting the initial commit though. Just thought I would point out that the latter seems more reliable.

jthill Over a year ago

@Treebranch this could happen if you have commits with odd timestamps. adding --topo-order to the rev-list should fix that, though I think the --max=parents=0 answer is best.

Hans Ginzel Over a year ago

Some commands, e.g. rebase, support the --root option for starting at the root commit.

Robert Munteanu · Accepted Answer · 2009-06-17 12:54:12Z

47

git rev-list HEAD | tail -n 1 is a more stable option.

answered Jun 17, 2009 at 12:54

Robert Munteanu

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3 Comments

Jakub Narębski Over a year ago

This would return one of tail commits; there can be more than one root (parentless) commit

protoEvangelion Over a year ago

This answer worked perfectly and only returned one commit sha whereas git rev-list --max-parents=0 HEAD returned 3 commits.

Johny Skovdal Over a year ago

tail is also not a command that's there by default in windows - works in GitBash on windows though. :)

Clay Bridges · Accepted Answer · 2020-08-14 15:05:02Z

16

Not sure what you're trying to do here, but some git commands take --root as an option, in order to reference the root of the commit tree, e.g.

git rebase --interactive --root main

answered Aug 14, 2020 at 15:05

Clay Bridges

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Comments

abh · Accepted Answer · 2021-02-12 17:59:08Z

8

Assuming the first parent of a merge is the main line of development:

git rev-list --reverse --topo-order --first-parent HEAD | sed 1q

answered Feb 12, 2021 at 17:59

abh

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1 Comment

David Jones Over a year ago

If i could award bonus points for using sed instead of head then I would. sed 1q can be pointlessly shortened to sed q by the way.

emi · Accepted Answer · 2022-08-10 20:01:38Z

2

Taken into account there could be multiple initial (orphan) but those commits still reachable from any of the refs it's possible to use:

git rev-list --all --max-parents=0

or

git rev-list --reflog --max-parents=0

But if it's required to find root commits including non-reachable ones, git fsck could be used:

git fsck --root --no-dangling

The --no-dangling option suppresses warning messages about dangling commits making it easier to process output in scripts.

edited Aug 10, 2022 at 20:01

emi

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answered Jun 14, 2022 at 11:41

reddot

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Eng_Farghly · Accepted Answer · 2022-12-11 08:53:04Z

1

To get first commit on the repository, run this command:

 git rev-list --oneline HEAD | tail -n 1

answered Dec 11, 2022 at 8:53

Eng_Farghly

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Carlos Gant · Accepted Answer · 2026-01-24 22:40:25Z

0

git rebase --root --exec 'git commit --amend --no-edit --reset-author'

answered Jan 24 at 22:40

Carlos Gant

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1 Comment

Dan Getz Jan 24 at 23:34

Does this have anything to do with the question it was posted as an answer to? If so, please edit to explain, because as is it looks unrelated.

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