lib/omb-prompt-base: Set a timeout on git commands

The calculate of git_summary_status can be extremely expensive for large
repos. This results in the shell becoming unresponsive.

We now set a timeout of 0.2 seconds to make sure we always have
a responsive shell.

Fixes ohmybash#172

lib/omb-prompt-base.sh

@@ -36,13 +36,15 @@ SCM_GIT_SHOW_CURRENT_USER=${SCM_GIT_SHOW_CURRENT_USER:=false}
 SCM_GIT_SHOW_MINIMAL_INFO=${SCM_GIT_SHOW_MINIMAL_INFO:=false}
 
 SCM_GIT='git'
+
 SCM_GIT_CHAR='±'
 SCM_GIT_DETACHED_CHAR='⌿'
 SCM_GIT_AHEAD_CHAR="↑"
 SCM_GIT_BEHIND_CHAR="↓"
 SCM_GIT_UNTRACKED_CHAR="?:"
 SCM_GIT_UNSTAGED_CHAR="U:"
 SCM_GIT_STAGED_CHAR="S:"
+SCM_GIT_TIMEOUT="0.2"
 
 SCM_HG='hg'
 SCM_HG_CHAR='☿'
@@ -105,7 +107,24 @@ function _omb_prompt_format {
 }
 
 function _omb_prompt_git {
-  command git "$@"
+  run_with_timeout $SCM_GIT_TIMEOUT command git "$@"
+}
+
+function run_with_timeout() {
+    # Runs the given command with the given timeout
+    # $1 Timeout in seconds
+    # $@ Command to be executed.
+    local TIME=$1
+    shift
+    local CMD=$@
+    local TIMEOUT=
+    if which timeout &> /dev/null; then
+      TIMEOUT=timeout
+    elif which gtimeout &> /dev/null; then
+      TIMEOUT=gtimeout
+    fi
+
+    $TIMEOUT ${TIME} ${CMD}
 }
 
 function scm {