git: use `master` if it exists, otherwise use `main`

See https://github.com/ohmyzsh/ohmyzsh/pull/9049#issuecomment-654537347

Co-authored-by: Yufan You <ouuansteve@gmail.com>

plugins/git/README.md

@@ -183,8 +183,8 @@ plugins=(... git)
 
 Following the recent push for removing racially-charged words from our technical vocabulary, the git plugin favors using
 a branch name other than `master`. In this case, we favor the shorter, neutral and descriptive term `main`. This means
-that any aliases and functions that previously used `master`, will use `main` if that branch exists. We do this via the
-function `git_main_branch`.
+that any aliases and functions that previously used `master`, will use `main` if `master` doesn't exist. We do this via
+the function `git_main_branch`.
 
 ### Deprecated aliases
 
@@ -214,7 +214,7 @@ These are aliases that have been removed, renamed, or otherwise modified in a wa
 | current_branch         | Return the name of the current branch                                        |
 | git_current_user_name  | Returns the `user.name` config value                                         |
 | git_current_user_email | Returns the `user.email` config value                                        |
-| git_main_branch        | Returns the name of the main branch: `main` if it exists, `master` otherwise |
+| git_main_branch        | Returns the name of the main branch: `master` if it exists, `main` otherwise |
 
 ### Work in Progress (WIP)
 

plugins/git/git.plugin.zsh

@@ -27,10 +27,10 @@ function work_in_progress() {
 
 # Check if main exists and use instead of master
 function git_main_branch() {
-  if [[ -n "$(git branch --list main)" ]]; then
-    echo main
-  else
+  if [[ -n "$(git branch --list master)" ]]; then
     echo master
+  else
+    echo main
   fi
 }