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Mermaid!

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Co-Authored-By: Sergio Padrino <1083228+sergiou87@users.noreply.github.com>
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63
docs/learn-more/unreachable-commits.md
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@ -2,31 +2,29 @@
In Git, every commit will have at least one parent commit except the very first. Additionally, a repository may have any number of branches that begin at any particular commit. Because of this we can create a graph of the history of a commit by following the path from one commit's parent to the another. Given a branch `main`, whose initial commit is `A`, and we add commit `B` and `C`, the resulting graph would be as follows:
```
main
C
|
B
|
A
```mermaid
gitGraph
commit id: "A"
commit id: "B"
commit id: "C"
```
Since we can follow the graph from `C` to `A`, that means that `A` is **reachable** by or from `C`. This as known as following the ancestral path of `C`.
## Unreachable Commits
Now, if we create a new branch called `feature-branch` from `C` and commit `D` and `E` and then return to `main` and commit `F`. We would have the resulting graph:
```
main
F
| E
| | <-- feature-branch
| D
| /
C
|
B
|
A
```mermaid
gitGraph
commit id: "A"
commit id: "B"
commit id: "C"
branch feature-branch
checkout feature-branch
commit id: "D"
commit id: "E"
checkout main
commit id: "F"
```
In the above example, `B` is reachable by `F` through the ancestral path of `F`-> `C` -> `B`, and `B` is reachable by `E` through `E` -> `D` -> `C` -> `B`. However, there is no such path to get to `E` or `D` from `F`. Thus, `E` and `D` are **unreachable** from `F`.
@ -36,20 +34,19 @@ Some Git commands use the ancestral path to determine what to show. One of those
## Merge Commits
Now, let's say that we merge the `feature-branch` into our `main` branch. Our graph becomes:
```
main
G
| \
F |
| E
| | <-- feature-branch
| D
| /
C
|
B
|
A
```mermaid
gitGraph
commit id: "A"
commit id: "B"
commit id: "C"
branch feature-branch
checkout feature-branch
commit id: "D"
commit id: "E"
checkout main
commit id: "F"
merge feature-branch tag: "G"
```
Still `E` and `D` are unreachable by `F`. But, you may think "I merged the `feature-branch` into `main`, I should be able to see changes from `E` and `D`." This is true if you start at a commit that has them in its ancestral path. That is `G` and it is known as a **merge commit**, and it is special in that it has two parents. The first is `F` as the last commit of the branch being merged into, and `E` as the last commit of the branch being merged. Now, all the commits in this graph are ancestors of `G`. Thus, if we were to execute `git diff B..G`. We will see changes of all ancestral paths of `G` to `B`. Those paths are `G` -> `F` -> `C` -> `B` and `G`-> `E` -> `D` -> `C` -> `B`. Therefore we will see changes from `G`, `F`, `E`, `D`, and `C`.