Adds a progress bar reporting files analyzed, number of violations and number of errors to CLI in real time. Interleaves with other output to avoid breaking the progress bar.

PMD is frequently run on CLI, and can have lengthy execution times. Currently, the feedback it provides during runtime is limited, especially when the output is specified as a file. This means that users (and also IDE plugins) had little idea of the live progress of the PMD analysis. Our contribution was then as follows:

• Add a CLI progress bar that updates live as files are analyzed, including live stats such as number of rule violations and errors.
  • This entailed making a new AnalysisListener that gets notified of execution events from multiple threads and uses Atomic counters to aaggregate statistics
• Make this progress bar properly interleave with other CLI output, including errors and rule violations if the output is specified as text.
  • This was unexpectedly difficult. To make this work, the progress bar output must dynamicly change whether or not is it output with a trailing carraige return depending on what else is being output by the system.

Adds to the PMD documentation website a table of contents that follows scrolling behaviour and is responsive for small screen devices.

This pull request was started based on an issue that noted the documentation website had a lot of empty space on large screens, and could benefit from having a table of contents appear there instead of only at the top. As such, what we implemented:

• Generating a table of contents based on the webpage contents
• Adding this either to a floating and sticky table of contents div in the free space
  • Or, if the screen width was too small, just add this table of contents in line with the documentation article and don’t make it sticky.

This PR fosters the “Edit me on github” button on the documentation page of PMD by: adding the button at the bottom with some more explaining text, and adding a smaller button in the section heading line of each section. After the changes were reviewed, there were some extra requested changes: add a header to each page with a home button, the current page, and an “Edit me” button; put the bottom text with the edit button in the footer of the page; use pencils instead of buttons in the header sections; and remove the anchor links and edit buttons from the toc by calling the toc first.

Adding release date under the version number header on the navigation bar and modifying the CSS styling of this local part on the docs page. In the file sidebar.html under the folder docs/_includes/, the version number and the release date are retrieved from the attributes site.pmd.version and site.pmd.date, respectively. The local rendering result looks nice. This pull request is opened but not merged yet.

Fixes the table of contents on the PMD documentation website (that we added) by making it scrollable when a page contains too many subheadings.

This fixes an issue we introduced into the code base with our first merged pull request to add a table of contents to the documentation website. We had not accounted for the edge case of documentation pages with many subheadings, such as the index of code metrics page. In this PR we fixed that issue by: set a fixed max height of the table of contents; add overflow behaviour to the table of contents div.