Repository: spyder-ide/spyder

Issue:
Cancelling "Save as" leads to modified marker (that cannot be undone)
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### Issue Report Checklist

* [x] Searched the [issues page](https://github.com/spyder-ide/spyder/issues?q=is%3Aissue) for similar reports
* [ ] Read the relevant sections of the [Spyder Troubleshooting Guide](https://github.com/spyder-ide/spyder/wiki/Troubleshooting-Guide-and-FAQ) and followed its advice
* [ ] Reproduced the issue after updating with ``conda update spyder`` (or ``pip``, if not using Anaconda)
* [ ] Could not reproduce inside ``jupyter qtconsole`` (if console-related)
* [x] Tried basic troubleshooting (if a bug/error)
    * [x] Restarted Spyder
    * [ ] Reset preferences with ``spyder --reset``
    * [ ] Reinstalled the latest version of [Anaconda](https://www.anaconda.com/download/)
    * [ ] Tried the other applicable steps from the Troubleshooting Guide
* [x] Completed the **Problem Description**, **Steps to Reproduce** and **Version** sections below


## Problem Description
Minor issue, but a bit annoying at times. When cancelling a "Save as" file dialog, the file is marked as modified. (There is no way to undo this, which is maybe not a problem as such, more that it is my standard way to try to remove modified markers that shouldn't be there...) The tab can be closed without any warnings about unsaved modifications though.

![cancelsaveas](https://user-images.githubusercontent.com/8114497/61569766-49635980-aa89-11e9-8662-0a2da3f19bb2.gif)

### What steps reproduce the problem?

1. Select "Save as" 
2. Press cancel in the file dialog

### What is the expected output? What do you see instead?
No modified marker in the file tab (and "Save" not activated etc)

## Versions
<!--- You can get this information from Help > About Spyder...
or (if Spyder won't launch) the "conda list" command
from the Anaconda Prompt/Terminal/command line. --->

* Spyder version: 4.0.0.dev0
* Python version: 3.7.3
* Qt version: 5.9.6
* PyQt version: 5.9.2
* Operating System name/version: Windows 10

### Dependencies
<!--- Please go to the menu entry Help > Dependencies,
press the Copy to clipboard button and paste below --->

```
pygments >=2.0    :  2.4.2 (OK)
qdarkstyle >=2.6.4:  2.7 (OK)
sphinx >=0.6.6    :  2.1.2 (OK)
pyls >=0.27.0     :  0.27.0 (OK)
nbconvert >=4.0   :  5.5.0 (OK)
pandas >=0.13.1   :  0.24.2 (OK)
numpy >=1.7       :  1.16.4 (OK)
sympy >=0.7.3     :  1.4 (OK)
cython >=0.21     :  0.29.11 (OK)
qtconsole >=4.5.0 :  4.5.1 (OK)
IPython >=4.0     :  7.5.0 (OK)
matplotlib >=2.0.0:  3.1.0 (OK)
pylint >=0.25     :  2.3.1 (OK)

```



Discussion:

Resolving patch:
diff --git a/spyder/plugins/editor/widgets/editor.py b/spyder/plugins/editor/widgets/editor.py
--- a/spyder/plugins/editor/widgets/editor.py
+++ b/spyder/plugins/editor/widgets/editor.py
@@ -2001,6 +2001,7 @@ def save_as(self, index=None):
             self.set_stack_index(new_index)
             return ok
         else:
+            finfo.newly_created = False
             return False
 
     def save_copy_as(self, index=None):


Test patch: