Allow setting a default name when creating new branches

docs/Config.md

@@ -323,6 +323,9 @@ git:
     # Replace directive. E.g. for 'feature/AB-123' to start the commit message with 'AB-123 ' use "[$1] "
     replace: ""
 
+  # See https://github.com/jesseduffield/lazygit/blob/master/docs/Config.md#predefined-branch-name-prefix
+  branchPrefix: ""
+
   # If true, parse emoji strings in commit messages e.g. render :rocket: as 🚀
   # (This should really be under 'gui', not 'git')
   parseEmoji: false
@@ -885,6 +888,21 @@ git:
       replace: '[$1] '
 ```
 
+## Predefined branch name prefix
+
+In situations where certain naming pattern is used for branches, this can be used to populate new branch creation with a static prefix.
+
+Example:
+
+Some branches:
+- jsmith/AB-123
+- cwilson/AB-125
+
+```yaml
+git:
+  branchPrefix: "firstlast/"
+```
+
 ## Custom git log command
 
 You can override the `git log` command that's used to render the log of the selected branch like so: