diff --git a/.gitignore b/.gitignore
index df3f70056fa..82a8b476b0a 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,5 +1,6 @@
 # ScanCode special files
 /SCANCODE_DEV_MODE
+/SCANCODE_GIT_MODE
 
 # Python compiled files
 *.py[cod]
diff --git a/MANIFEST.in b/MANIFEST.in
index 3c1c088160b..d68be2d33d1 100644
--- a/MANIFEST.in
+++ b/MANIFEST.in
@@ -2,7 +2,6 @@ graft src
 graft etc
 graft thirdparty
 graft samples
-
 graft tests
 
 prune src/scancode_toolkit.egg-info
@@ -27,8 +26,10 @@ include scancode
 include scancode.bat
 include extractcode
 include extractcode.bat
+include .travis.yml
+include appveyor.yml
 
-include .travis.yml appveyor.yml
 exclude SCANCODE_DEV_MODE
+exclude SCANCODE_GIT_MODE
 
 global-exclude *.py[co] __pycache__ *.*~
diff --git a/etc/conf/base.py b/etc/conf/base.py
index 6f1b431d30a..9222e4e3cea 100644
--- a/etc/conf/base.py
+++ b/etc/conf/base.py
@@ -23,11 +23,11 @@ def unsupported(platform):
 
 sys_platform = str(sys.platform).lower()
 if 'linux' in sys_platform:
-    os = 'linux'
+    platform = 'linux'
 elif'win32' in sys_platform:
-    os = 'win'
+    platform = 'win'
 elif 'darwin' in sys_platform:
-    os = 'mac'
+    platform = 'mac'
 else:
     unsupported(sys_platform)
 
@@ -38,9 +38,24 @@ def unsupported(platform):
     'mac': ['64',],
 }
 
-arches = supported_combos[os]
+arches = supported_combos[platform]
 if arch not in arches:
-    unsupported(os + arch)
+    unsupported(platform + arch)
+
+
+def clear_dev_mode():
+    """
+    Remove any stale development tag file from previous configure runs.
+    """
+    import os
+    from scancode import root_dir
+    try:
+        os.remove(os.path.join(root_dir, 'SCANCODE_DEV_MODE'))
+    except OSError:
+        pass
+
+
+clear_dev_mode()
 
 
 """
diff --git a/etc/conf/dev/base.py b/etc/conf/dev/base.py
index 31c5fa3a1e6..ba4435f6afe 100644
--- a/etc/conf/dev/base.py
+++ b/etc/conf/dev/base.py
@@ -7,14 +7,11 @@
 
 
 def setup_dev_mode():
-    """
-    Create the development mode tag file. In development mode, ScanCode does
-    not rely on license data to remain untouched and will always check the
-    license index cache for consistency, rebuilding it if necessary.
-    """
     from scancode import root_dir
     with open(os.path.join(root_dir, 'SCANCODE_DEV_MODE'), 'wb') as sdm:
-        sdm.write('This is a tag file to notify that ScanCode is used in development mode.')
+        sdm.write('This is a tag file to notify that ScanCode is used in development mode. '
+                  'In this mode, ScanCode does not rely on license data to remain untouched and will '
+                  'always check the license index cache for consistency, rebuilding it if necessary.')
 
 
 setup_dev_mode()
diff --git a/etc/configure.py b/etc/configure.py
index 44cada3448a..6eee4426462 100644
--- a/etc/configure.py
+++ b/etc/configure.py
@@ -213,7 +213,7 @@ def create_virtualenv(std_python, root_dir, tpp_dirs, quiet=False):
 
 def activate(root_dir):
     """ Activate a virtualenv in the current process."""
-    print("* Activating ...")
+    print("* Activating...")
     bin_dir = os.path.join(root_dir, 'bin')
     activate_this = os.path.join(bin_dir, 'activate_this.py')
     with open(activate_this) as f:
@@ -365,6 +365,8 @@ def get_conf_files(config_dir_paths, root_dir, file_names=requirements):
             abs_path = os.path.join(root_dir, path)
             if os.path.exists(abs_path):
                 configs.append(path)
+                print('Using configuration directory:\n'
+                      '  %(path)s' % locals())
         else:
             print()
             print('WARNING: Skipping missing Configuration directory:\n'
diff --git a/etc/release/MANIFEST.in.release b/etc/release/MANIFEST.in.release
index 4168afdafd0..cd3ca1cd12e 100644
--- a/etc/release/MANIFEST.in.release
+++ b/etc/release/MANIFEST.in.release
@@ -26,7 +26,10 @@ include scancode
 include scancode.bat
 include extractcode
 include extractcode.bat
-include .travis.yml appveyor.yml
+include .travis.yml
+include appveyor.yml
 
 exclude SCANCODE_DEV_MODE
+exclude SCANCODE_GIT_MODE
+
 global-exclude *.py[co] __pycache__ *.*~
diff --git a/scancode b/scancode
index a863caee25e..cf69839728b 100755
--- a/scancode
+++ b/scancode
@@ -105,10 +105,33 @@ _canonicalize_file_path() {
 SCANCODE_BIN="$( realpath "${BASH_SOURCE[0]}" )"
 SCANCODE_ROOT_DIR="$( cd "$( dirname "${SCANCODE_BIN}" )" && pwd )"
 
+SCANCODE_CONFIG_DIR="etc/conf"
+
+GIT_STATUS=$(git -C "$SCANCODE_ROOT_DIR" status --porcelain 2> /dev/null)
+if [ $? -eq 0 ]; then
+    # This is a Git working tree, check whether it is clean.
+    if [ -z "$GIT_STATUS" ]; then
+        # This is a clean working tree, check whether configure has been run
+        # before for this commit.
+        GIT_COMMIT_CONFIGURED=$(cat "$SCANCODE_ROOT_DIR/SCANCODE_GIT_MODE" 2> /dev/null)
+        GIT_COMMIT_HEAD=$(git -C "$SCANCODE_ROOT_DIR" rev-parse HEAD)
+        if [ "$GIT_COMMIT_CONFIGURED" != "$GIT_COMMIT_HEAD" ]; then
+            echo "* (Re-)Configuring ScanCode because Git commits have changed..."
+            CONFIGURE_QUIET=1 $SCANCODE_ROOT_DIR/configure $SCANCODE_CONFIG_DIR
+        fi
+        echo $GIT_COMMIT_HEAD > "$SCANCODE_ROOT_DIR/SCANCODE_GIT_MODE"
+    else
+        echo "* (Re-)Configuring ScanCode because Git working tree is not clean..."
+        CONFIGURE_QUIET=1 $SCANCODE_ROOT_DIR/configure $SCANCODE_CONFIG_DIR
+    fi
+else
+    rm -f "$SCANCODE_ROOT_DIR/SCANCODE_GIT_MODE"
+fi
+
 SCANCODE_CONFIGURED_PYTHON=$SCANCODE_ROOT_DIR/bin/python
 if [ ! -f "$SCANCODE_CONFIGURED_PYTHON" ]; then
     echo "* Configuring ScanCode for first use..."
-    CONFIGURE_QUIET=1 $SCANCODE_ROOT_DIR/configure etc/conf
+    CONFIGURE_QUIET=1 $SCANCODE_ROOT_DIR/configure $SCANCODE_CONFIG_DIR
 fi
 
 $SCANCODE_ROOT_DIR/bin/scancode "$@"