CODEWITHSUNDEEP
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StaticCrazee
StaticCrazee

Reputation: 297

Relative Commit References

I was looking through a Git course (on relative commits) when I encountered the following:

* 9ec05ca (HEAD -> master) Revert "Set page heading to "Quests & Crusades""
* db7e87a Set page heading to "Quests & Crusades"
*   796ddb0 Merge branch 'heading-update'
|\  
| * 4c9749e (heading-update) Set page heading to "Crusade"
* | 0c5975a Set page heading to "Quest"
|/  
*   1a56a81 Merge branch 'sidebar'
|\  
| * f69811c (sidebar) Update sidebar with favorite movie
| * e6c65a6 Add new sidebar content
* | e014d91 (footer) Add links to social media
* | 209752a Improve site heading for SEO
* | 3772ab1 Set background color for page
|/  
* 5bfe5e7 Add starting HTML structure
* 6fa5f34 Add .gitignore file
* a879849 Add header to blog
* 94de470 Initial commit

Referring to commits relative to HEAD (SHA 9ec05ca), the instructor wrote the following:

HEAD^ is the db7e87a commit
HEAD~1 is also the db7e87a commit
HEAD^^ is the 796ddb0 commit
HEAD~2 is also the 796ddb0 commit
HEAD^^^ is the 0c5975a commit
HEAD~3 is also the 0c5975a commit
HEAD^^^2 is the 4c9749e commit (this is the grandparent's (HEAD^^) second parent (^2))

My confusion lies with HEAD's great-grandparent (HEAD^^^) which I think should be 4c9749e or 1a56a81 (parents of the merge 796ddb0). I've looked around everywhere (including What's the difference between HEAD^ and HEAD~ in Git?). But it only made the instructor's answer more confusing.

Upvotes: 2

Views: 3059

Answers (1)

Sazzadur Rahaman
Sazzadur Rahaman

Reputation: 7116

Confusion about the parents of the merge 796ddb0 (you think it should be 4c9749e or 1a56a81)

No. When you are merging the branch heading-update back, by this time the original head moved from 1a56a81 to 0c5975a. So the merge commit is actually merging two current heads (0c5975a and 4c9749e). As a result the parents of 796ddb0 are 0c5975a and 4c9749e.

Now, if you are convinced, then we can visualize the graph as following (I just replaced stars (*) with commit ids),

              9ec05ca
                 |
              db7e87a
                 |
              796ddb0
                /\
               /  \
         0c5975a  4c9749e
              \    /
               \  /
              1a56a81

The above graph leads to the following conclusion.

HEAD^^^ --> ((HEAD^1)^1)^1
        --> ((db7e87a)^1)^1
        --> (796ddb0)^1
        --> 0c5975a

Upvotes: 6

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