The Gitiles source browser automatically renders *.md Markdown files into HTML for simplified documentation.
Access controls for documentation is identical to source code.
Documentation stored with source files shares the same permissions. Documentation stored in a separate Git repository can use different access controls. If Gerrit Code Review is being used, branch level read permissions can be used to grant or restrict access to any documentation branches.
Files named README.md are automatically displayed below the file's directory listing. For the top level directory this mirrors the standard GitHub presentation.
We recommend that Git repositories have an up-to-date top-level README.md file.
Gitiles supports the core Markdown syntax described in Markdown Basics. Additional extensions are supported to more closely match GitHub Flavored Markdown and simplify documentation writing.
Paragraphs are one or more lines of consecutive text, followed by one or more blank lines. Line breaks within a paragraph are ignored by the parser, allowing authors to line-wrap text at any comfortable column width.
Documentation writing can be fun and profitable by helping users to learn and solve problems. After documentation is written, it needs to be published on the web where it can be easily accessed for reading.
Headings can be indicated by starting the line with one or more # marks. The number of # used determines the depth of the heading in the document outline. Headings 1 through 6 (######) are supported.
# A level one (H1) heading ## A level two (H2) heading ### A level three (H3) heading
Headings can also use the less popular two line ====== and ------ forms to create H1 and H2 level headers:
A first level header ==================== A second level header ---------------------
This form is discouraged as maintaining the length of the === or --- lines to match the preceding line can be tedious work that is unnecessary with the # headers.
A bullet list:
* Fruit
* Orange
* Pear
* Cake
will render into HTML as:
The second level items (above Orange, Pear) must be indented with more spaces than the item they are nested under. Above 2 spaces were used.
A numbered list:
1. Fruit
1. Orange
2. Pear
5. Cake
will render into HTML as:
List items will be renumbered sequentially by the browser, which is why 5 above displays as 2. Even with this feature it is a good idea to maintain list item numbers in the source Markdown to simplify reading the source file.
Like bullet lists, numbered lists can be nested by using more leading space than the prior list item.
Simple tables are supported with column alignment. The first line is the header row and subsequent lines are data rows:
| Food | Calories | Tasty? | |-------|---------:|:------:| | Apple | 95 | Yes | | Pear | 102 | Yes | | Hay | 977 | | [Food and its benefits]
will render as:
| Food | Calories | Tasty? |
|---|---|---|
| Apple | 95 | Yes |
| Pear | 102 | Yes |
| Hay | 977 |
[Food and its benefits]
Placing : in the separator line indicates how the column should be aligned. A colon on the left side is a left-aligned column; a colon on the right-most side is right-aligned; a colon on both sides is center-aligned.
An optional table title can be placed under the table in brackets ([...]).
Cells may span multiple columns and include formatting accepted within paragraphs such as emphasis, images or links:
| | Grouping ||
| First Header | Second Header | Third Header |
| ------------ | :-----------: | -----------: |
| Content | Long Cell ||
| Content | Cell 2 | Cell 3 |
the above table was created by:
| | Grouping || | First Header | Second Header | Third Header | | ------------ | :-----------: | -----------: | | Content | *Long Cell* || | Content | **Cell 2** | Cell 3 |
Empty table cells are indicated by whitespace between the column dividers (| |) while multiple column cells omit the whitespace.
Emphasize paragraph text with italic and bold styles. Either _ or * can be used for italic (1 character) and bold text (2 characters). This allows styles to be mixed within a statement:
Emphasize paragraph text with *italic* and **bold** text. **It is _strongly_ encouraged to review documentation for typos.**
It is strongly encouraged to review documentation for typos.
Emphasis within_words_is_ignored which helps write technical documentation. Literal *bold* can be forced by prefixing the opening * with \ such as \*bold*.
Text can be struck out within a paragraph:
Text can be ~~struck out~~ within a paragraph.
Note two tildes are required (~~) on either side of the struck out section of text.
‘Single’, “double” and <> quotes in paragraph text are replaced with smart quotes. Apostrophes (this doc's text), ellipses (“...”) and dashes (“--” and “---”) are also replaced with HTML entities to make the documentation appear typeset.
To force use of the ASCII characters prefix with , for example \' for a ' normal single quote.
Blockquoted text can be used to stand off text obtained from another source:
Sir Winston Churchill once said: > A lie gets halfway around the world before the truth has a > chance to get its pants on.
renders as:
Sir Winston Churchill once said:
A lie gets halfway around the world before the truth has a chance to get its pants on.
Use backticks to markup inline code within a paragraph:
Use `backticks` to markup inline code within a paragraph.
Create a fenced code block using three backticks before and after a block of code, preceeded and followed by blank lines:
This is a simple hello world program in C:
#include <stdio.h>
int main() { printf(“Hello, World.\n”); return 0; }
To compile it use `gcc hello.c`.
Text within a fenced code block is taken verbatim and is not processed for Markdown markup.
A horizontal rule can be inserted using GitHub style -- surrounded by blank lines. Alternatively repeating - or * and space on a line will also create a horizontal rule:
-- - - - - * * * *
Wrap text in [brackets] and the link destination in parens (http://...) such as:
Visit [this site](http://example.com/) for more examples.
Links can also use references to obtain URLs from elsewhere in the same document. This style can be useful if the same URL needs to be mentioned multiple times, is too long to cleanly place within text, or the link is within a table cell:
Search for [markdown style][1] examples. [1]: https://www.google.com/?gws_rd=ssl#q=markdown+style+guide
References can be simplified if the text alone is sufficient:
Visit [Google] to search the web. [Google]: https://www.google.com/
Automatic hyperlinking can be used where the link text should obviously also be the URL:
Use https://www.google.com/ to search the web.
Well formed URLs beginning with https://, http://, and mailto: are used as written for the link's destination. Malformed URLs may be replaced with #zSoyz to prevent browser evaluation of dangerous content.
HTML escaping of URL characters such as & is handled internally by the parser/formatter. Documentation writers should insert the URL literally and allow the parser and formatter to make it HTML safe.
Relative links such as ../src/api.md are resolved relative to the current markdown's file path within the Git repository. Absolute links such as /src/api.md are resolved relative to the top of the enclosing Git repository, but within the same branch or Git commit. Links may point to any file in the repository. A link to a *.md file will present the rendered markdown, while a link to a source file will display the syntax highlighted source.
Similar to links but begin with ! to denote an image reference:
For images the text in brackets will be included as the alt text for screen readers.
Well formed image URLs beginning with https:// and http:// will be used as written for the <img src="..."> attribute. Malformed URLs will be replaced with a broken data: reference to prevent browsers from trying to load a bad destination.
Relative and absolute links to image files within the Git repository (such as ../images/banner.png) are resolved during rendering by inserting the base64 encoding of the image using a data: URI. Only PNG (*.png), JPEG (*.jpg or *.jpeg) and GIF (*.gif) image formats are supported when referenced from the Git repository.
The Gitiles markdown.imageLimit configuration variable sets an upper byte limit for inserted image files. Unsupported extensions or files larger than this threshold (default 256K) will display a broken image.
Inline image caching
Gitiles allows browsers to locally cache rendered markdown pages. Cache invalidation is triggered by the markdown file being modified and having a different SHA-1 in Git. Inlined images may need a documentation file update to be refreshed when viewed through unstable URLs like /docs/+/master/index.md.
HTML tags are not supported. HTML will be dropped on the floor by the parser with no warnings, and no output from that section of the document.
There is a small exception for the <iframe> element, see HTML IFrame below.
Gitiles includes additional extensions to the Markdown language that make documentation writing for the web easier without using raw HTML.
Place [TOC] surrounded by blank lines to insert a generated table of contents extracted from the H1, H2, and H3 headers used within the document:
# Title [TOC] ## Section 1 Blah blah... ## Section 2 Go on...
H1 headers are omitted from the table of contents if there is only one level one header present. This allows H1 to be used as the document title without creating an unnecessary entry in the table of contents.
Element ids to create anchors are automatically generated by filtering the text of the header. For example above Section 1 will have the anchor #Section-1. To create an anchor letters and digits are used (after removing accents), spaces are replaced with -, and other characters are replaced with _. Changing the title of a section will (most likely) change its anchor.
Similar to fenced code blocks these blocks start and end with ***, are surrounded by blank lines, and include the type of block on the opening line.
*** note **Warning:** watch out for nested formatting. ***
*** aside An aside can stand off less interesting text. ***
*** promo Promotions can raise awareness of an important concept. ***
Gitiles markdown includes support for up to 12 columns of text across the width of the page. By default space is divided equally between the columns.
A column layout is denoted by a block starting and ending with the sequence |||---|||. Within the layout a new column is started for each header or note/promo/aside block and all text and formatting flow into that column until a new column is started.
|||---||| #### Columns can save space. #### Prettify the page layout. *** promo #### Can be trendy. *** |||---|||
Column spans can be specified on the first line as a comma separated list. In the example below the first column is 4 wide or 4/12ths of the page width, the second is 2 wide (or 2/12ths) and the final column is 6 wide (6/12ths or 50%) of the page.
|||---||| 4,2,6
An empty column can be inserted by prefixing its width with :, for example shifting content onto the right by padding 6 columns on the left:
|||---||| :6,3 # Right |||---|||
renders as:
Although HTML is stripped the parser has special support for a limited subset of <iframe> elements:
<iframe src="https://example.com/embed" height="200px" width="400px"></iframe>
The parser allows whitespace including newlines between attributes, but strictly limits the supported attribute set to:
src : An https:// or http:// URL of the page to embed inside of an iframe at this position in the document. Malformed URLs will cause the iframe to be silently dropped. (required)
height : CSS pixel height such as 250px defining the amount of vertical space to give to the embedded content. Only px units are supported; a malformed dimension will drop the iframe. (required)
width : CSS pixel width such as 250px or a precentage such as 80% defining the amount of horizontal space to give to the embedded content. Only px units or % are supported; a malformed dimension will drop the iframe. (required)
frameborder : By default a border is drawn around the iframe by the browser. The border can be hidden by adding frameborder="0" to the iframe tag. (optional)
Embedded source URLs must also be whitelisted by the Gitiles markdown.allowiframe configuration variable.
Gitiles includes additional support to create functional documentation sites served directly from Git repositories.
A top level navigation bar is automatically included on all pages if there is a navbar.md file present in the top of the repository. This file should be a simple bulleted list of links to include in the navigation bar.
* [Home](/index.md) * [Markdown](/docs/markdown.md) * [Configuration](/docs/configuration.md)
Links are resolved relative to the current page, not navbar.md. Links to other files within the repository should use absolute paths to ensure they are resolved correctly from any Markdown file within the repository.
A site wide banner is displayed on all Markdown pages if navbar.md includes a H1 header. The text of the header is display on the left side of the banner.
# Gitiles * [Home](/index.md)
An optional logo image is displayed in the banner to the left of the site title if a [logo] reference exists in navbar.md. This image should be no taller than 45 px.
# Gitiles [logo]: /images/site_logo.png
See images above for acceptable URLs and how repository relative paths are handled by inline data URIs.
Both the site logo (if present) and site title are wrapped in a link if the [home] reference is declared in navbar.md. This is typically also used in the outline for the navigation bar:
# Gitiles * [Home][home] * [Markdown](/docs/markdown.md) [home]: /index.md
Titles for pages are extracted from the first H1 heading appearing in the document. This is traditionally placed on the first line of the markdown file, e.g.:
# Markdown
The title is included in the HTML <title> element and also in the right side of the banner if navbar.md defines a site title.