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Finding Commits Before a Merge Point in Git

Index

This guide explains how to use Git’s relative reference syntax to locate commits before a merge point in a branch’s history.

Consider the following commit history for the master branch, which includes a merge from the temp branch:

$ git log --oneline --graph
* f121040 (HEAD -> master) 5
*   b4d4109 Merge branch 'temp'
|\
| * 9463330 (temp) b
| * 1c57deb a
* | 76b4746 4
* | a69fb73 3
|/
* 837f54f 2
* 518575a 1

The temp branch, with commits a and b, was merged into master. The commit 2 is the divergence point (where temp branched off from master), and the merge commit is between commits 4 and 5.

%%{init: { 'gitGraph': {'mainBranchName': 'master'} }}%% gitGraph BT: commit id: "1" commit id: "2" branch temp checkout temp commit id: "a" commit id: "b" checkout master commit id: "3" commit id: "4" merge temp id: "merge commit" commit id: "5"

The current HEAD is at commit 5:

$ git show HEAD --oneline --no-patch
f121040 (HEAD -> master) 5

%%{init: { 'gitGraph': {'mainBranchName': 'master'} }}%% gitGraph BT: commit id: "1" commit id: "2" branch temp checkout temp commit id: "a" commit id: "b" checkout master commit id: "3" commit id: "4" merge temp id: "merge commit" commit id: "5" type: HIGHLIGHT

In Git, you can use the ^ operator to reference a commit’s parent. For example, to view the direct parent of the current HEAD:

$ git show HEAD^ --oneline --no-patch
b4d4109 Merge branch 'temp'

%%{init: { 'gitGraph': {'mainBranchName': 'master'} }}%% gitGraph BT: commit id: "1" commit id: "2" branch temp checkout temp commit id: "a" commit id: "b" checkout master commit id: "3" commit id: "4" merge temp id: "merge commit" type: HIGHLIGHT commit id: "5"

This output confirms that the parent of commit 5 is the merge commit, where temp was merged into master.

To navigate further back, you can chain ^ operators. For example, to reach the parent of the merge commit along the main branch:

$ git show HEAD^^ --oneline --no-patch
76b4746 4

%%{init: { 'gitGraph': {'mainBranchName': 'master'} }}%% gitGraph BT: commit id: "1" commit id: "2" branch temp checkout temp commit id: "a" commit id: "b" checkout master commit id: "3" commit id: "4" type: HIGHLIGHT merge temp id: "merge commit" commit id: "5"

The ^ operator is equivalent to ^1, so HEAD^1^1 can be simplified to HEAD^^. Alternatively, you can use the ~ operator to specify the nth ancestor along the first parent: HEAD~n. The following commands are equivalent:

$ git show HEAD^1^1 --oneline --no-patch
76b4746 4
$ git show HEAD^^ --oneline --no-patch
76b4746 4
$ git show HEAD~2 --oneline --no-patch
76b4746 4

A merge commit has multiple parents. In this case, the merge commit (b4d4109) has two parents: 4 (first parent, from master) and b (second parent, from temp). The commands above follow the first parent (4). To access the second parent (b), use ^2:

$ git show HEAD^^2 --oneline --no-patch
9463330 (temp) b

%%{init: { 'gitGraph': {'mainBranchName': 'master'} }}%% gitGraph BT: commit id: "1" commit id: "2" branch temp checkout temp commit id: "a" commit id: "b" type: HIGHLIGHT checkout master commit id: "3" commit id: "4" merge temp id: "merge commit" commit id: "5"

To navigate further back along the temp branch to commit a, use:

$ git show HEAD^^2^ --oneline --no-patch
1c57deb a

Alternatively, these commands are equivalent:

$ git show HEAD^^2~1 --oneline --no-patch
1c57deb a
$ git show HEAD~1^2~1 --oneline --no-patch
1c57deb a

%%{init: { 'gitGraph': {'mainBranchName': 'master'} }}%% gitGraph BT: commit id: "1" commit id: "2" branch temp checkout temp commit id: "a" type: HIGHLIGHT commit id: "b" checkout master commit id: "3" commit id: "4" merge temp id: "merge commit" commit id: "5"

By combining ^ and ~ with parent indices, you can precisely navigate to any commit in the history relative to the current HEAD.

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