diff --git a/lib/git.zsh b/lib/git.zsh
index f7d4738ca..ffc7c01a1 100644
--- a/lib/git.zsh
+++ b/lib/git.zsh
@@ -1,9 +1,20 @@
+# The git prompt's git commands are read-only and should not interfere with
+# other processes. This environment variable is equivalent to running with `git
+# --no-optional-locks`, but falls back gracefully for older versions of git.
+# See git(1) for and git-status(1) for a description of that flag.
+#
+# We wrap in a local function instead of exporting the variable directly in
+# order to avoid interfering with manually-run git commands by the user.
+function __git_prompt_git() {
+  GIT_OPTIONAL_LOCKS=0 command git "$@"
+}
+
 # Outputs current branch info in prompt format
 function git_prompt_info() {
   local ref
-  if [[ "$(command git config --get oh-my-zsh.hide-status 2>/dev/null)" != "1" ]]; then
-    ref=$(command git symbolic-ref HEAD 2> /dev/null) || \
-    ref=$(command git rev-parse --short HEAD 2> /dev/null) || return 0
+  if [[ "$(__git_prompt_git config --get oh-my-zsh.hide-status 2>/dev/null)" != "1" ]]; then
+    ref=$(__git_prompt_git symbolic-ref HEAD 2> /dev/null) || \
+    ref=$(__git_prompt_git rev-parse --short HEAD 2> /dev/null) || return 0
     echo "$ZSH_THEME_GIT_PROMPT_PREFIX${ref#refs/heads/}$(parse_git_dirty)$ZSH_THEME_GIT_PROMPT_SUFFIX"
   fi
 }
@@ -13,7 +24,7 @@ function parse_git_dirty() {
   local STATUS
   local -a FLAGS
   FLAGS=('--porcelain')
-  if [[ "$(command git config --get oh-my-zsh.hide-dirty)" != "1" ]]; then
+  if [[ "$(__git_prompt_git config --get oh-my-zsh.hide-dirty)" != "1" ]]; then
     if [[ "${DISABLE_UNTRACKED_FILES_DIRTY:-}" == "true" ]]; then
       FLAGS+='--untracked-files=no'
     fi
@@ -27,7 +38,7 @@ function parse_git_dirty() {
         FLAGS+="--ignore-submodules=${GIT_STATUS_IGNORE_SUBMODULES:-dirty}"
         ;;
     esac
-    STATUS=$(command git status ${FLAGS} 2> /dev/null | tail -n1)
+    STATUS=$(__git_prompt_git status ${FLAGS} 2> /dev/null | tail -n1)
   fi
   if [[ -n $STATUS ]]; then
     echo "$ZSH_THEME_GIT_PROMPT_DIRTY"
@@ -39,10 +50,10 @@ function parse_git_dirty() {
 # Gets the difference between the local and remote branches
 function git_remote_status() {
     local remote ahead behind git_remote_status git_remote_status_detailed
-    remote=${$(command git rev-parse --verify ${hook_com[branch]}@{upstream} --symbolic-full-name 2>/dev/null)/refs\/remotes\/}
+    remote=${$(__git_prompt_git rev-parse --verify ${hook_com[branch]}@{upstream} --symbolic-full-name 2>/dev/null)/refs\/remotes\/}
     if [[ -n ${remote} ]]; then
-        ahead=$(command git rev-list ${hook_com[branch]}@{upstream}..HEAD 2>/dev/null | wc -l)
-        behind=$(command git rev-list HEAD..${hook_com[branch]}@{upstream} 2>/dev/null | wc -l)
+        ahead=$(__git_prompt_git rev-list ${hook_com[branch]}@{upstream}..HEAD 2>/dev/null | wc -l)
+        behind=$(__git_prompt_git rev-list HEAD..${hook_com[branch]}@{upstream} 2>/dev/null | wc -l)
 
         if [[ $ahead -eq 0 ]] && [[ $behind -eq 0 ]]; then
             git_remote_status="$ZSH_THEME_GIT_PROMPT_EQUAL_REMOTE"
@@ -71,11 +82,11 @@ function git_remote_status() {
 # it's not a symbolic ref, but in a Git repo.
 function git_current_branch() {
   local ref
-  ref=$(command git symbolic-ref --quiet HEAD 2> /dev/null)
+  ref=$(__git_prompt_git symbolic-ref --quiet HEAD 2> /dev/null)
   local ret=$?
   if [[ $ret != 0 ]]; then
     [[ $ret == 128 ]] && return  # no git repo.
-    ref=$(command git rev-parse --short HEAD 2> /dev/null) || return
+    ref=$(__git_prompt_git rev-parse --short HEAD 2> /dev/null) || return
   fi
   echo ${ref#refs/heads/}
 }
@@ -83,8 +94,8 @@ function git_current_branch() {
 
 # Gets the number of commits ahead from remote
 function git_commits_ahead() {
-  if command git rev-parse --git-dir &>/dev/null; then
-    local commits="$(git rev-list --count @{upstream}..HEAD 2>/dev/null)"
+  if __git_prompt_git rev-parse --git-dir &>/dev/null; then
+    local commits="$(__git_prompt_git rev-list --count @{upstream}..HEAD 2>/dev/null)"
     if [[ -n "$commits" && "$commits" != 0 ]]; then
       echo "$ZSH_THEME_GIT_COMMITS_AHEAD_PREFIX$commits$ZSH_THEME_GIT_COMMITS_AHEAD_SUFFIX"
     fi
@@ -93,8 +104,8 @@ function git_commits_ahead() {
 
 # Gets the number of commits behind remote
 function git_commits_behind() {
-  if command git rev-parse --git-dir &>/dev/null; then
-    local commits="$(git rev-list --count HEAD..@{upstream} 2>/dev/null)"
+  if __git_prompt_git rev-parse --git-dir &>/dev/null; then
+    local commits="$(__git_prompt_git rev-list --count HEAD..@{upstream} 2>/dev/null)"
     if [[ -n "$commits" && "$commits" != 0 ]]; then
       echo "$ZSH_THEME_GIT_COMMITS_BEHIND_PREFIX$commits$ZSH_THEME_GIT_COMMITS_BEHIND_SUFFIX"
     fi
@@ -103,21 +114,21 @@ function git_commits_behind() {
 
 # Outputs if current branch is ahead of remote
 function git_prompt_ahead() {
-  if [[ -n "$(command git rev-list origin/$(git_current_branch)..HEAD 2> /dev/null)" ]]; then
+  if [[ -n "$(__git_prompt_git rev-list origin/$(git_current_branch)..HEAD 2> /dev/null)" ]]; then
     echo "$ZSH_THEME_GIT_PROMPT_AHEAD"
   fi
 }
 
 # Outputs if current branch is behind remote
 function git_prompt_behind() {
-  if [[ -n "$(command git rev-list HEAD..origin/$(git_current_branch) 2> /dev/null)" ]]; then
+  if [[ -n "$(__git_prompt_git rev-list HEAD..origin/$(git_current_branch) 2> /dev/null)" ]]; then
     echo "$ZSH_THEME_GIT_PROMPT_BEHIND"
   fi
 }
 
 # Outputs if current branch exists on remote or not
 function git_prompt_remote() {
-  if [[ -n "$(command git show-ref origin/$(git_current_branch) 2> /dev/null)" ]]; then
+  if [[ -n "$(__git_prompt_git show-ref origin/$(git_current_branch) 2> /dev/null)" ]]; then
     echo "$ZSH_THEME_GIT_PROMPT_REMOTE_EXISTS"
   else
     echo "$ZSH_THEME_GIT_PROMPT_REMOTE_MISSING"
@@ -127,62 +138,50 @@ function git_prompt_remote() {
 # Formats prompt string for current git commit short SHA
 function git_prompt_short_sha() {
   local SHA
-  SHA=$(command git rev-parse --short HEAD 2> /dev/null) && echo "$ZSH_THEME_GIT_PROMPT_SHA_BEFORE$SHA$ZSH_THEME_GIT_PROMPT_SHA_AFTER"
+  SHA=$(__git_prompt_git rev-parse --short HEAD 2> /dev/null) && echo "$ZSH_THEME_GIT_PROMPT_SHA_BEFORE$SHA$ZSH_THEME_GIT_PROMPT_SHA_AFTER"
 }
 
 # Formats prompt string for current git commit long SHA
 function git_prompt_long_sha() {
   local SHA
-  SHA=$(command git rev-parse HEAD 2> /dev/null) && echo "$ZSH_THEME_GIT_PROMPT_SHA_BEFORE$SHA$ZSH_THEME_GIT_PROMPT_SHA_AFTER"
+  SHA=$(__git_prompt_git rev-parse HEAD 2> /dev/null) && echo "$ZSH_THEME_GIT_PROMPT_SHA_BEFORE$SHA$ZSH_THEME_GIT_PROMPT_SHA_AFTER"
 }
 
 # Get the status of the working tree
 function git_prompt_status() {
+  emulate -L zsh
+
   local INDEX STATUS
-  INDEX=$(command git status --porcelain -b 2> /dev/null)
+  INDEX=$(__git_prompt_git status --porcelain -b 2> /dev/null) || return 0
   STATUS=""
-  if $(echo "$INDEX" | command grep -E '^\?\? ' &> /dev/null); then
+  if [[ "${INDEX}" =~ $'(^|\n)\\?\\? ' ]]; then
     STATUS="$ZSH_THEME_GIT_PROMPT_UNTRACKED$STATUS"
   fi
-  if $(echo "$INDEX" | grep '^A  ' &> /dev/null); then
-    STATUS="$ZSH_THEME_GIT_PROMPT_ADDED$STATUS"
-  elif $(echo "$INDEX" | grep '^M  ' &> /dev/null); then
-    STATUS="$ZSH_THEME_GIT_PROMPT_ADDED$STATUS"
-  elif $(echo "$INDEX" | grep '^MM ' &> /dev/null); then
+  if [[ "${INDEX}" =~ $'(^|\n)(A |M |MM) ' ]]; then
     STATUS="$ZSH_THEME_GIT_PROMPT_ADDED$STATUS"
   fi
-  if $(echo "$INDEX" | grep '^ M ' &> /dev/null); then
-    STATUS="$ZSH_THEME_GIT_PROMPT_MODIFIED$STATUS"
-  elif $(echo "$INDEX" | grep '^AM ' &> /dev/null); then
-    STATUS="$ZSH_THEME_GIT_PROMPT_MODIFIED$STATUS"
-  elif $(echo "$INDEX" | grep '^MM ' &> /dev/null); then
-    STATUS="$ZSH_THEME_GIT_PROMPT_MODIFIED$STATUS"
-  elif $(echo "$INDEX" | grep '^ T ' &> /dev/null); then
+  if [[ "${INDEX}" =~ $'(^|\n)([ AM]M| T) ' ]]; then
     STATUS="$ZSH_THEME_GIT_PROMPT_MODIFIED$STATUS"
   fi
-  if $(echo "$INDEX" | grep '^R  ' &> /dev/null); then
+  if [[ "${INDEX}" =~ $'(^|\n)R  ' ]]; then
     STATUS="$ZSH_THEME_GIT_PROMPT_RENAMED$STATUS"
   fi
-  if $(echo "$INDEX" | grep '^ D ' &> /dev/null); then
-    STATUS="$ZSH_THEME_GIT_PROMPT_DELETED$STATUS"
-  elif $(echo "$INDEX" | grep '^D  ' &> /dev/null); then
-    STATUS="$ZSH_THEME_GIT_PROMPT_DELETED$STATUS"
-  elif $(echo "$INDEX" | grep '^AD ' &> /dev/null); then
+  if [[ "${INDEX}" =~ $'(^|\n)([A ]D|D ) ' ]]; then
     STATUS="$ZSH_THEME_GIT_PROMPT_DELETED$STATUS"
   fi
-  if $(command git rev-parse --verify refs/stash >/dev/null 2>&1); then
+  if $(__git_prompt_git rev-parse --verify refs/stash >/dev/null 2>&1); then
     STATUS="$ZSH_THEME_GIT_PROMPT_STASHED$STATUS"
   fi
-  if $(echo "$INDEX" | grep '^UU ' &> /dev/null); then
+  if [[ "${INDEX}" =~ $'(^|\n)UU ' ]]; then
     STATUS="$ZSH_THEME_GIT_PROMPT_UNMERGED$STATUS"
   fi
-  if $(echo "$INDEX" | grep '^## [^ ]\+ .*ahead' &> /dev/null); then
+  if [[ "${INDEX}" =~ $'(^|\n)## [^ ]\+ .*ahead' ]]; then
     STATUS="$ZSH_THEME_GIT_PROMPT_AHEAD$STATUS"
   fi
-  if $(echo "$INDEX" | grep '^## [^ ]\+ .*behind' &> /dev/null); then
+  if [[ "${INDEX}" =~ $'(^|\n)## [^ ]\+ .*behind' ]]; then
     STATUS="$ZSH_THEME_GIT_PROMPT_BEHIND$STATUS"
   fi
-  if $(echo "$INDEX" | grep '^## [^ ]\+ .*diverged' &> /dev/null); then
+  if [[ "${INDEX}" =~ $'(^|\n)## [^ ]\+ .*diverged' ]]; then
     STATUS="$ZSH_THEME_GIT_PROMPT_DIVERGED$STATUS"
   fi
   echo $STATUS
@@ -191,20 +190,20 @@ function git_prompt_status() {
 # Outputs the name of the current user
 # Usage example: $(git_current_user_name)
 function git_current_user_name() {
-  command git config user.name 2>/dev/null
+  __git_prompt_git config user.name 2>/dev/null
 }
 
 # Outputs the email of the current user
 # Usage example: $(git_current_user_email)
 function git_current_user_email() {
-  command git config user.email 2>/dev/null
+  __git_prompt_git config user.email 2>/dev/null
 }
 
 # Output the name of the root directory of the git repository
 # Usage example: $(git_repo_name)
 function git_repo_name() {
   local repo_path
-  if repo_path="$(git rev-parse --show-toplevel 2>/dev/null)" && [[ -n "$repo_path" ]]; then
+  if repo_path="$(__git_prompt_git rev-parse --show-toplevel 2>/dev/null)" && [[ -n "$repo_path" ]]; then
     echo ${repo_path:t}
   fi
 }