Previous commit ~

Previous commit ~#

You can use the <commit>~n construction to reference a commit that is n steps back in the commit chain.

Basic example#

In the following example:

  • Two commits were created;

  • git log shows that HEAD refer to second commit;

  • git show HEAD~1 show the idea:

    • git show is a command that displays information about a passed commit;

    • HEAD~1 is passed as an argument to git show, which means that a commit back from commit HEAD refers to;

    • So we got information about first commit, which is correct, it is a commit back from second commit.

%%bash
mkdir operations_examples
cd operations_examples
git init &> /dev/null

touch file1
git add --all
git commit -am "first commit" &> /dev/null

touch file2
git add --all
git commit -am "second commit" &> /dev/null

echo "=====git log====="
git log --oneline --decorate
echo "=====git show====="
git show HEAD~1

cd ..
rm -r operations_examples

=====git log=====
e94d28e (HEAD -> master) second commit
73e5ca8 first commit
=====git show=====
commit 73e5ca80b04925b1f03d6b9e0b164a796439ff71
Author: Fedor Kobak <kobfedsur@gmail.com>
Date:   Sun Sep 10 10:25:44 2023 +0300

    first commit

diff --git a/file1 b/file1
new file mode 100644
index 0000000..e69de29

Use hash#

I was wondering if it is possible to use the commit hash in this construct, i.e. <hash>~1? Yes, you can! The following example confirms it:

  • Created two commits, first commit and second commit;

  • Stored hash of second commit in variable

  • I used variable with syntax ~1;

  • All is well - I got info on first commit, which is one before second commit.

%%bash
mkdir operations_examples
cd operations_examples
git init &> /dev/null

touch file1
git add --all
git commit -am "first commit" &> /dev/null

touch file2
git add --all
git commit -am "second commit" &> /dev/null
second_hash=$(git rev-parse HEAD)

echo "=====git log====="
git log --oneline --decorate
echo "=====git show====="
git show $second_hash~1

cd ..
rm -r operations_examples

=====git log=====
e79a082 (HEAD -> master) second commit
3d2a63f first commit
=====git show=====
commit 3d2a63fcbd20eb9730ae250cef9ab6133e60ef19
Author: Fedor Kobak <kobfedsur@gmail.com>
Date:   Sun Sep 10 10:35:54 2023 +0300

    first commit

diff --git a/file1 b/file1
new file mode 100644
index 0000000..e69de29