Show more information on the Patch tab?

**Is your feature request related to a problem? Please describe.**
When we are on the "commit" panel, we can see the Patch tab, showing the commit id, author, email, date, etc.
Suppose the commit id is `127b2be4`, we can use
```
git show --pretty=fuller 127b2be4
```
to obtain more detailed information about this commit.

I know we can custom the git log command through
```yaml
git:
branchLogCmd: "git log --graph --color=always --pretty=medium --oneline {{branchName}} --"
```
Can we show more information on the patch tab in a similar way?

**Describe the solution you'd like**
Provide a options like:
```yaml
git:
showCmd: "git show --pretty=fuller {{ .SelectedLocalCommit.Sha }}"
```