diff --git a/fish/includes/git.fish b/fish/includes/git.fish
index 6228362..2d9175b 100644
--- a/fish/includes/git.fish
+++ b/fish/includes/git.fish
@@ -61,6 +61,11 @@ function git-require-clean --description 'Require a clean git worktree'
     end
 end
 
+function git-ref-exists --description 'Return success if a git ref exists'
+    test (count $argv) -eq 1; or return 1
+    command git rev-parse --verify --quiet "$argv[1]" >/dev/null 2>&1
+end
+
 function git-main-branch --description 'Print the repository main branch name'
     set -l remote_head (command git symbolic-ref --quiet --short refs/remotes/origin/HEAD 2>/dev/null)
     if test -n "$remote_head"
@@ -69,11 +74,11 @@ function git-main-branch --description 'Print the repository main branch name'
     end
 
     for branch in main master trunk develop
-        if command git show-ref --verify --quiet refs/heads/$branch
+        if git-ref-exists refs/heads/$branch
             printf '%s\n' "$branch"
             return 0
         end
-        if command git show-ref --verify --quiet refs/remotes/origin/$branch
+        if git-ref-exists refs/remotes/origin/$branch
             printf '%s\n' "$branch"
             return 0
         end
@@ -102,7 +107,7 @@ function br --description 'Switch to an existing branch, or create one from upda
     set -l branch "$argv[1]"
     git-require-clean; or return 1
 
-    if command git show-ref --verify --quiet "refs/heads/$branch"; or command git show-ref --verify --quiet "refs/remotes/origin/$branch"
+    if git-ref-exists "refs/heads/$branch"; or git-ref-exists "refs/remotes/origin/$branch"
         command git checkout "$branch"
         return $status
     end
diff --git a/powershell.ps1 b/powershell.ps1
index fc69de5..d929e30 100644
--- a/powershell.ps1
+++ b/powershell.ps1
@@ -525,6 +525,16 @@ function git-require-clean {
     if (-not (Test-GitCleanWorktree)) { return 1 }
 }
 
+function Test-GitRef {
+    param([Parameter(Mandatory = $true)][string]$Ref)
+
+    $gitExe = Get-ExternalCommandPath git
+    if (-not $gitExe) { return $false }
+
+    & $gitExe rev-parse --verify --quiet $Ref *> $null
+    return $LASTEXITCODE -eq 0
+}
+
 function git-main-branch {
     $remoteHead = Invoke-RawGit symbolic-ref --quiet --short refs/remotes/origin/HEAD 2>$null
     if ($LASTEXITCODE -eq 0 -and $remoteHead) {
@@ -532,10 +542,8 @@ function git-main-branch {
     }
 
     foreach ($branch in @('main', 'master', 'trunk', 'develop')) {
-        Invoke-RawGit show-ref --verify --quiet "refs/heads/$branch" *> $null
-        if ($LASTEXITCODE -eq 0) { return $branch }
-        Invoke-RawGit show-ref --verify --quiet "refs/remotes/origin/$branch" *> $null
-        if ($LASTEXITCODE -eq 0) { return $branch }
+        if (Test-GitRef "refs/heads/$branch") { return $branch }
+        if (Test-GitRef "refs/remotes/origin/$branch") { return $branch }
     }
 
     Write-Error 'Could not determine main branch.'
@@ -556,11 +564,7 @@ function br {
     param([Parameter(Mandatory = $true)][string]$Branch)
     if (-not (Test-GitCleanWorktree)) { return 1 }
 
-    Invoke-RawGit show-ref --verify --quiet "refs/heads/$Branch" *> $null
-    $hasLocal = $LASTEXITCODE -eq 0
-    Invoke-RawGit show-ref --verify --quiet "refs/remotes/origin/$Branch" *> $null
-    $hasRemote = $LASTEXITCODE -eq 0
-    if ($hasLocal -or $hasRemote) {
+    if ((Test-GitRef "refs/heads/$Branch") -or (Test-GitRef "refs/remotes/origin/$Branch")) {
         Invoke-RawGit checkout $Branch
         return $LASTEXITCODE
     }
diff --git a/scripts/includes/later/git.zsh b/scripts/includes/later/git.zsh
index 8eb1453..252713b 100644
--- a/scripts/includes/later/git.zsh
+++ b/scripts/includes/later/git.zsh
@@ -58,6 +58,11 @@ git-require-clean() {
     fi
 }
 
+git-ref-exists() {
+    [[ $# -eq 1 ]] || return 1
+    command git rev-parse --verify --quiet "$1" >/dev/null 2>&1
+}
+
 git-main-branch() {
     local remote_head
     remote_head=$(command git symbolic-ref --quiet --short refs/remotes/origin/HEAD 2>/dev/null)
@@ -68,11 +73,11 @@ git-main-branch() {
 
     local branch
     for branch in main master trunk develop; do
-        if command git show-ref --verify --quiet "refs/heads/$branch"; then
+        if git-ref-exists "refs/heads/$branch"; then
             echo "$branch"
             return 0
         fi
-        if command git show-ref --verify --quiet "refs/remotes/origin/$branch"; then
+        if git-ref-exists "refs/remotes/origin/$branch"; then
             echo "$branch"
             return 0
         fi
@@ -101,7 +106,7 @@ br() {
     local branch="$1"
     git-require-clean || return 1
 
-    if command git show-ref --verify --quiet "refs/heads/$branch" || command git show-ref --verify --quiet "refs/remotes/origin/$branch"; then
+    if git-ref-exists "refs/heads/$branch" || git-ref-exists "refs/remotes/origin/$branch"; then
         command git checkout "$branch"
         return $?
     fi