tasks: add get time last modified util

- use in image test container tasks to display
  to the last build/plotly.js bundle time.

Author: etpinard

tasks/baseline.js

@@ -1,9 +1,17 @@
+var constants = require('./util/constants');
 var common = require('./util/common');
 var containerCommands = require('./util/container_commands');
 
+var msg = [
+    'Generating baseline image(s) using build/plotly.js from',
+    common.getTimeLastModified(constants.pathToPlotlyBuild),
+    '\n'
+].join(' ');
+
 var cmd = containerCommands.getRunCmd(
     process.env.CIRCLECI,
     'node test/image/make_baseline.js ' + process.argv.slice(2).join(' ')
 );
 
+console.log(msg);
 common.execCmd(cmd);

tasks/test_export.js

@@ -1,9 +1,17 @@
+var constants = require('./util/constants');
 var common = require('./util/common');
 var containerCommands = require('./util/container_commands');
 
+var msg = [
+    'Running image export tests using build/plotly.js from',
+    common.getTimeLastModified(constants.pathToPlotlyBuild),
+    '\n'
+].join(' ');
+
 var cmd = containerCommands.getRunCmd(
     process.env.CIRCLECI,
     'node test/image/export_test.js ' + process.argv.slice(2).join(' ')
 );
 
+console.log(msg);
 common.execCmd(cmd);

tasks/test_image.js

@@ -1,9 +1,17 @@
+var constants = require('./util/constants');
 var common = require('./util/common');
 var containerCommands = require('./util/container_commands');
 
+var msg = [
+    'Running image comparison tests using build/plotly.js from',
+    common.getTimeLastModified(constants.pathToPlotlyBuild),
+    '\n'
+].join(' ');
+
 var cmd = containerCommands.getRunCmd(
     process.env.CIRCLECI,
     'node test/image/compare_pixels_test.js ' + process.argv.slice(2).join(' ')
 );
 
+console.log(msg);
 common.execCmd(cmd);

tasks/util/common.js

@@ -46,6 +46,17 @@ exports.formatTime = function(date) {
     ].join(' ');
 };
 
+exports.getTimeLastModified = function(filePath) {
+    if(!exports.doesFileExist(filePath)) {
+        throw new Error(filePath + ' does not exist');
+    }
+
+    var stats = fs.statSync(filePath),
+        formattedTime = exports.formatTime(stats.mtime);
+
+    return formattedTime;
+};
+
 exports.touch = function(filePath) {
     fs.closeSync(fs.openSync(filePath, 'w'));
 };