diff --git a/gitrisky/cli.py b/gitrisky/cli.py
index 38dbd8e..1032d7f 100644
--- a/gitrisky/cli.py
+++ b/gitrisky/cli.py
@@ -14,7 +14,9 @@ def cli():
 
 
 @cli.command()
-def train():
+@click.option('-p', '--pattern', required=False,
+              help="Bug fix pattern. Ex. BUG,FIX", type=str)
+def train(pattern=None):
     """Train a git commit bug risk model.
 
     This will save a pickled sklearn model to a file in the toplevel directory
@@ -23,7 +25,10 @@ def train():
 
     # get the features and labels by parsing the git logs
     features = get_features()
-    labels = get_labels()
+    if pattern is not None:
+        labels = get_labels(pattern.split(','))
+    else:
+        labels = get_labels(pattern)
 
     # instantiate and train a model
     model = create_model()
diff --git a/gitrisky/gitcmds.py b/gitrisky/gitcmds.py
index 72593a3..c0f7841 100644
--- a/gitrisky/gitcmds.py
+++ b/gitrisky/gitcmds.py
@@ -3,7 +3,7 @@
 import re
 
 from collections import defaultdict
-from subprocess import check_output
+from subprocess import check_output, CalledProcessError
 
 
 def _run_bash_command(bash_cmd):
@@ -20,7 +20,11 @@ def _run_bash_command(bash_cmd):
         The resulting stdout output.
     """
 
-    stdout = check_output(bash_cmd.split()).decode('utf-8').rstrip('\n')
+    try:
+        stdout = check_output(bash_cmd.split()).decode('utf-8').rstrip('\n')
+    except CalledProcessError as err:
+        print('Failed to execute bash command: {!r}'.format(str(bash_cmd)))
+        exit(1)
 
     return stdout
 
@@ -80,7 +84,7 @@ def get_git_log(commit=None):
     return stdout
 
 
-def get_bugfix_commits():
+def get_bugfix_commits(pattern=None):
     """Get the commits whose commit messages contain BUG or FIX.
 
     Returns
@@ -89,8 +93,12 @@ def get_bugfix_commits():
         A list of commit hashes.
     """
 
+    if pattern is None:
+        pattern = ("BUG", "FIX")
+
     # TODO: add option to specify custom bugfix tags
-    bash_cmd = "git log -i --all --grep BUG --grep FIX --pretty=format:%h"
+    bash_cmd = "git log -i --all --grep {} --grep {} --pretty=format:%h"\
+        .format(pattern[0], pattern[1])
 
     stdout = _run_bash_command(bash_cmd)
 
diff --git a/gitrisky/parsing.py b/gitrisky/parsing.py
index 4e5af0a..39d3571 100644
--- a/gitrisky/parsing.py
+++ b/gitrisky/parsing.py
@@ -135,7 +135,7 @@ def get_features(commit=None):
     return feats
 
 
-def get_labels():
+def get_labels(pattern=None):
     """Get a label for each commit indicating whether it introduced a bug.
 
     Returns
@@ -147,7 +147,7 @@ def get_labels():
 
     feats = get_features()
 
-    fix_commits = get_bugfix_commits()
+    fix_commits = get_bugfix_commits(pattern)
 
     bug_commits = link_fixes_to_bugs(fix_commits)