I put a private repository on Bitbucket.org, and this project needs some documentations that involve a lot of math stuff. I want to use Bitbucket Wiki and edit it in Markdown but how should I also. Personal site of Christian Specht, software developer from Kerpen, Germany. Bitbucket can parse and display Markdown, reStructuredText, Textile, and plain text README files. With a syntax like Markdown, you can emphasize text, include screen captures, and more. For a tutorial on Bitbucket's Markdown support and syntax examples, see our Markdown demo repository.

Feb 02, 2021 Bitbucket Data Center and Server uses Markdown for formatting text, as specified in CommonMark (with a few extensions). You can use Markdown in the following places: any pull request's descriptions or comments, or; in README files (if they have the.md file extension). Use Control-Shift-P or Command-Shift-P to preview your markdown. Markdown syntax. It seems that Bitbucket Markdown does not support html-entities like  , and literally displays it as  , not as non-breaking space. This is really awkward: I wrote a huge Readme.md with hundreds of  s, and in IntelliJ IDEA preview all works as expected. But on Bitbucket the layout displays as totally broken.

For quite some time now, the content of the project pages on my site (this one, for example) was coming directly from the respective Markdown readme file on Bitbucket (this one, for example).

I already wrote multiple times about how my approach how to get this to work - here, here and a bit here.

Until now, the code where all the magic happened looked like this:

It just loads the Markdown file from $url, converts the content to HTML and returns the HTML.
The problem is that it’s pulling the Markdown file directly from Bitbucket - on each request.

To make things worse, it’s not only the Markdown files: each readme contains at least one image (the project logo on the top), and some of the readmes have even more images - screenshots, for example.
All these images are directly coming from the Bitbucket repository as well…because in the Markdown files, I’m doing this:

In other words:
If you visited https://christianspecht.de/bitbucket-backup/, this happened:

Of course, all this together takes quite long:

It could be worse, but >700ms isn’t quick either.
So I tried to cache everything on my web server to avoid the requests to Bitbucket.

Caching the Markdown/HTML file

I’m using PHP to load the Markdown files (because my webspace runs PHP anyway), but I have nearly no actual coding experience with it. So I looked around how others do caching in PHP, and found this tutorial.

Based on the code there, here is a new version of the GetMarkdown function, now with caching.
Note that this is not the complete version yet…the version shown here includes only the changes necessary to cache the Markdown file (but not the images):

Quite simple, actually.
The function now expects a second parameter where I’m just passing the title of the calling page (“Bitbucket Backup”, for example). After removing blanks and converting to lowercase, the title becomes the name of the cached HTML file: bitbucket-backup.html

If there already is an existing cache file that’s not too old, I load the HTML from there.
If not, I make a request to the passed URL, get the Markdown file, convert it to HTML, save the HTML in the cache folder and return it to the caller.

That works well, but fixes only half of the loading time problem, because the images are still requested from Bitbucket.

Caching the images

I knew what I wanted to do:

1. Search for <img> tags in the HTML
2. Get the image URL out there
3. Download the image from that URL on my server
4. Replace the original URL in the HTML by the “local” one on my server

I just didn’t know how to do it in PHP…so after some more googling, I added more code between these two lines from the last listing:

What I added was this:

The code gets the image URLs from the <img> tags and passes each one (together with the “blanks removed and lowercase” filename that was created for the cached HTML file) to the DownloadImage function:

This function downloads the image to my server, and returns the “new” URL of the image, which the calling code then replaces in the <img> tag.

To stick with the example from above: the logo from the top of Bitbucket Backup’s readme file will be located here after being copied to my server.
(if you click on the link now and the image is not there, it’s probably because I updated my site shortly before, and updating always empties the cache folder)

There’s one special case that wouldn’t work with the DownloadImage function listed above:
When the page contains two images from different URLs with identical file names, my current naming pattern $filename.'-'.basename($url) would lead to identical file names on my server as well, so the second image would overwrite the first one.
But I will neclect this, because I’m the only one with full control over the readme files, so I’ll just make sure that none of them has identical image file names.

I think there’s only one thing that needs additional explanation: the $html = preg_replace(...) line.
It’s there because DOMDocument has this (IMO unnecessary) feature that loadHTML always inserts <!DOCTYPE ...>, <html> and <body> tags whenever the loaded document is lacking them.
If someone doesn’t want that (like me), there seem to be only two options. I can’t use the first/proper one (yet) because the PHP version on my server is too old, so I have no other choice than to use the ugly-looking preg_replace(...) line.

Conclusion

The current (as of the time of writing this post) version of the code is here on Bitbucket.

After pushing it to the live site, I opened the site with Chrome’s developer tools again.

The first load actually took some more time than before:

(before the change, it was about 700 ms)

But I expected that, because of course that time also includes copying the images from Bitbucket onto my server.

On the other hand, all subsequent requests were way faster:

So the first visitor each day needs to wait a bit longer than before, but for everyone else the project pages are loading now nearly as fast as the other static pages (like this post).

Overview

Nearly all Markdown applications support the basic syntax outlined in John Gruber’s original design document. There are minor variations and discrepancies between Markdown processors — those are noted inline wherever possible.

Headings

To create a heading, add number signs (#) in front of a word or phrase. The number of number signs you use should correspond to the heading level. For example, to create a heading level three (<h3>), use three number signs (e.g., ### My Header).

Alternate Syntax

Alternatively, on the line below the text, add any number of characters for heading level 1 or -- characters for heading level 2.

Heading Best Practices

Markdown applications don’t agree on how to handle a missing space between the number signs (#) and the heading name. For compatibility, always put a space between the number signs and the heading name.

Paragraphs

To create paragraphs, use a blank line to separate one or more lines of text.

Paragraph Best Practices

Unless the paragraph is in a list, don’t indent paragraphs with spaces or tabs.

Line Breaks

To create a line break (<br>), end a line with two or more spaces, and then type return.

Line Break Best Practices

You can use two or more spaces (commonly referred to as “trailing whitespace”) for line breaks in nearly every Markdown application, but it’s controversial. It’s hard to see trailing whitespace in an editor, and many people accidentally or intentionally put two spaces after every sentence. For this reason, you may want to use something other than trailing whitespace for line breaks. Fortunately, there is another option supported by nearly every Markdown application: the <br> HTML tag.

For compatibility, use trailing white space or the <br> HTML tag at the end of the line.

There are two other options I don’t recommend using. CommonMark and a few other lightweight markup languages let you type a backslash () at the end of the line, but not all Markdown applications support this, so it isn’t a great option from a compatibility perspective. And at least a couple lightweight markup languages don’t require anything at the end of the line — just type return and they’ll create a line break.

Emphasis

You can add emphasis by making text bold or italic.

Bold

To bold text, add two asterisks or underscores before and after a word or phrase. To bold the middle of a word for emphasis, add two asterisks without spaces around the letters.

Bold Best Practices

Markdown applications don’t agree on how to handle underscores in the middle of a word. For compatibility, use asterisks to bold the middle of a word for emphasis.

Italic

To italicize text, add one asterisk or underscore before and after a word or phrase. To italicize the middle of a word for emphasis, add one asterisk without spaces around the letters.

Italic Best Practices

Markdown applications don’t agree on how to handle underscores in the middle of a word. For compatibility, use asterisks to italicize the middle of a word for emphasis.

Bold and Italic

To emphasize text with bold and italics at the same time, add three asterisks or underscores before and after a word or phrase. To bold and italicize the middle of a word for emphasis, add three asterisks without spaces around the letters.

Bold and Italic Best Practices

Markdown applications don’t agree on how to handle underscores in the middle of a word. For compatibility, use asterisks to bold and italicize the middle of a word for emphasis.

Blockquotes

To create a blockquote, add a > in front of a paragraph.

The rendered output looks like this:

Dorothy followed her through many of the beautiful rooms in her castle.

Blockquotes with Multiple Paragraphs

Blockquotes can contain multiple paragraphs. Add a > on the blank lines between the paragraphs.

The rendered output looks like this:

Dorothy followed her through many of the beautiful rooms in her castle.

The Witch bade her clean the pots and kettles and sweep the floor and keep the fire fed with wood.

Nested Blockquotes

Blockquotes can be nested. Add a >> in front of the paragraph you want to nest.

The rendered output looks like this:

Dorothy followed her through many of the beautiful rooms in her castle.

The Witch bade her clean the pots and kettles and sweep the floor and keep the fire fed with wood.

Blockquotes with Other Elements

Blockquotes can contain other Markdown formatted elements. Not all elements can be used — you’ll need to experiment to see which ones work.

The rendered output looks like this:

The quarterly results look great!

• Revenue was off the chart.
• Profits were higher than ever.

Everything is going according to plan.

Lists

You can organize items into ordered and unordered lists.

Ordered Lists

To create an ordered list, add line items with numbers followed by periods. The numbers don’t have to be in numerical order, but the list should start with the number one.

Ordered List Best Practices

CommonMark and a few other lightweight markup languages let you use a parenthesis ()) as a delimiter (e.g., 1) First item), but not all Markdown applications support this, so it isn’t a great option from a compatibility perspective. For compatibility, use periods only.

Unordered Lists

To create an unordered list, add dashes (-), asterisks (*), or plus signs (+) in front of line items. Indent one or more items to create a nested list.

Starting Unordered List Items With Numbers

If you need to start an unordered list item with a number followed by a period, you can use a backslash () to escape the period.

Unordered List Best Practices

Markdown applications don’t agree on how to handle different delimiters in the same list. For compatibility, don’t mix and match delimiters in the same list — pick one and stick with it.

Adding Elements in Lists

To add another element in a list while preserving the continuity of the list, indent the element four spaces or one tab, as shown in the following examples.

Paragraphs

The rendered output looks like this:

• This is the first list item.

• Here’s the second list item.

  I need to add another paragraph below the second list item.

• And here’s the third list item.

Blockquotes

The rendered output looks like this:

• This is the first list item.

• Here’s the second list item.

  A blockquote would look great below the second list item.

• And here’s the third list item.

Code Blocks

Code blocks are normally indented four spaces or one tab. When they’re in a list, indent them eight spaces or two tabs.

The rendered output looks like this:

1. Open the file.

2. Find the following code block on line 21:

3. Update the title to match the name of your website.

Images

The rendered output looks like this:

1. Open the file containing the Linux mascot.

2. Marvel at its beauty.

3. Close the file.

Lists

You can nest an unordered list in an ordered list, or vice versa.

The rendered output looks like this:

1. First item
2. Second item
3. Third item
   • Indented item
   • Indented item
4. Fourth item

Code

To denote a word or phrase as code, enclose it in backticks (`).

Escaping Backticks

If the word or phrase you want to denote as code includes one or more backticks, you can escape it by enclosing the word or phrase in double backticks (``).

Code Blocks

To create code blocks, indent every line of the block by at least four spaces or one tab.

The rendered output looks like this:

Horizontal Rules

To create a horizontal rule, use three or more asterisks (***), dashes (---), or underscores (___) on a line by themselves.

The rendered output of all three looks identical:

Horizontal Rule Best Practices

For compatibility, put blank lines before and after horizontal rules.

Links

To create a link, enclose the link text in brackets (e.g., [Duck Duck Go]) and then follow it immediately with the URL in parentheses (e.g., (https://duckduckgo.com)).

The rendered output looks like this:

My favorite search engine is Duck Duck Go.

Adding Titles

You can optionally add a title for a link. This will appear as a tooltip when the user hovers over the link. To add a title, enclose it in parentheses after the URL.

The rendered output looks like this:

My favorite search engine is Duck Duck Go.

URLs and Email Addresses

To quickly turn a URL or email address into a link, enclose it in angle brackets.

The rendered output looks like this:

https://www.markdownguide.org
fake@example.com

Formatting Links

To emphasize links, add asterisks before and after the brackets and parentheses. To denote links as code, add backticks in the brackets.

The rendered output looks like this:

I love supporting the EFF.
This is the Markdown Guide.
See the section on code.

Reference-style Links

Reference-style links are a special kind of link that make URLs easier to display and read in Markdown. Reference-style links are constructed in two parts: the part you keep inline with your text and the part you store somewhere else in the file to keep the text easy to read.

Formatting the First Part of the Link

The first part of a reference-style link is formatted with two sets of brackets. The first set of brackets surrounds the text that should appear linked. The second set of brackets displays a label used to point to the link you’re storing elsewhere in your document.

Although not required, you can include a space between the first and second set of brackets. The label in the second set of brackets is not case sensitive and can include letters, numbers, spaces, or punctuation.

This means the following example formats are roughly equivalent for the first part of the link:

• [hobbit-hole][1]
• [hobbit-hole] [1]

Formatting the Second Part of the Link

The second part of a reference-style link is formatted with the following attributes:

1. The label, in brackets, followed immediately by a colon and at least one space (e.g., [label]: ).
2. The URL for the link, which you can optionally enclose in angle brackets.
3. The optional title for the link, which you can enclose in double quotes, single quotes, or parentheses.

This means the following example formats are all roughly equivalent for the second part of the link:

• [1]: https://en.wikipedia.org/wiki/Hobbit#Lifestyle
• [1]: https://en.wikipedia.org/wiki/Hobbit#Lifestyle 'Hobbit lifestyles'
• [1]: https://en.wikipedia.org/wiki/Hobbit#Lifestyle 'Hobbit lifestyles'
• [1]: https://en.wikipedia.org/wiki/Hobbit#Lifestyle (Hobbit lifestyles)
• [1]: <https://en.wikipedia.org/wiki/Hobbit#Lifestyle> 'Hobbit lifestyles'
• [1]: <https://en.wikipedia.org/wiki/Hobbit#Lifestyle> 'Hobbit lifestyles'
• [1]: <https://en.wikipedia.org/wiki/Hobbit#Lifestyle> (Hobbit lifestyles)

You can place this second part of the link anywhere in your Markdown document. Some people place them immediately after the paragraph in which they appear while other people place them at the end of the document (like endnotes or footnotes).

An Example Putting the Parts Together

Say you add a URL as a standard URL link to a paragraph and it looks like this in Markdown:

Though it may point to interesting additional information, the URL as displayed really doesn’t add much to the existing raw text other than making it harder to read. To fix that, you could format the URL like this instead:

In both instances above, the rendered output would be identical:

In a hole in the ground there lived a hobbit. Not a nasty, dirty, wet hole, filled with the ends of worms and an oozy smell, nor yet a dry, bare, sandy hole with nothing in it to sit down on or to eat: it was a hobbit-hole, and that means comfort.

and the HTML for the link would be:

Link Best Practices

Markdown applications don’t agree on how to handle spaces in the middle of a URL. For compatibility, try to URL encode any spaces with %20.

Images

To add an image, add an exclamation mark (!), followed by alt text in brackets, and the path or URL to the image asset in parentheses. You can optionally add a title after the URL in the parentheses.

The rendered output looks like this:

Linking Images

To add a link to an image, enclose the Markdown for the image in brackets, and then add the link in parentheses.

The rendered output looks like this:

Escaping Characters

To display a literal character that would otherwise be used to format text in a Markdown document, add a backslash () in front of the character.

The rendered output looks like this:

* Without the backslash, this would be a bullet in an unordered list.

Characters You Can Escape

You can use a backslash to escape the following characters.

HTML

Many Markdown applications allow you to use HTML tags in Markdown-formatted text. This is helpful if you prefer certain HTML tags to Markdown syntax. For example, some people find it easier to use HTML tags for images. Using HTML is also helpful when you need to change the attributes of an element, like specifying the color of text or changing the width of an image.

To use HTML, place the tags in the text of your Markdown-formatted file.

The rendered output looks like this:

This word is bold. This word is italic.

HTML Best Practices

For security reasons, not all Markdown applications support HTML in Markdown documents. When in doubt, check your Markdown application’s documentation. Some applications support only a subset of HTML tags.

Use blank lines to separate block-level HTML elements like <div>, <table>, <pre>, and <p> from the surrounding content. Try not to indent the tags with tabs or spaces — that can interfere with the formatting.

You can’t use Markdown syntax inside block-level HTML tags. For example, <p>italic and **bold**</p> won’t work.

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