Optimize build process

[mmistakes]

TL/DR plan of attack: relegate Jekyll to Markdown parsing and building HTML and leave assets (CSS, JS, images, and fonts) to Gulp (or equivalent task runner).

• Replace jekyll-picture-tag with Gulp task.
• Replace jekyll-assets with Gulp tasks.
• Automate critical path CSS generation.
• Replace layout: compress with Gulp minify task.
• Replace Rake deploy tasks with Gulp.

The time to jekyll build and deploy the site has gotten out of hand the last couple of years. Test disabling various build tasks and plugins to determine offenders and investigate removing the dependency or developing a lighter weight alternative.

Made Mistakes Jekyll stats as of 8/23/2016:

• 1,014 source images to be generated into 5 sizes (1600, 1024, 768, 600, and 320 pixels)
• 7,795 image assets
• 991 posts
• 14 pages
• 3 sets of collections (47 documents)
• 535 comments stored as .yml
• Plugins (jekyll-picture-tag, sort_name filter, jekyll-archives, jekyll-assets, jekyll/tagging, jekyll-tagging-related_posts, jemoji)

Windows Test System:

• Lenovo ThinkStation E30
• Processor 3.30 GHz Intel Xeon E31245
• Memory 16 GB
• Intel SSDSA2BW160G3L 137GB
• Windows 7 Professional Service Pack 1
• ruby 2.2.4p230 [x64-mingw32]

Mac Test System:

• iMac 21.5-inch, Late 2013
• Processor 2.7 GHz Intel Core i5
• Memory 16 GB 1600 MHz DDR3
• 1.12 TB Fusion Drive
• OS X El Capitan 10.11.6
  -- ruby 2.1.0p0 (2013-12-25 revision 44422) [x86_64-darwin12.0]

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Initial build: bundle exec jekyll clean. Verify _site, .asset-cache, and any other .tmp folders and files have been removed.

To test build tasks, disable or remove from source and compute average time of 3 builds using bundle exec jekyll --profile.

task	task time (Windows)	task time (Mac)
Generate responsively sized page.image.feature photos	1288.289s	1429.255s
Minify HTML with layout: compress	39.348s	11.18s
Read /images/ and copy to _site/	32.385s	23.629s
Build tag pages with jekyll-archives	17.398s	9.994s
Build tag index page with sort_tag filter	2.62s	0.586s
List related posts with jekyll-tagging-related_posts, jekyll/tagging, and LSI: true	38.356s	17.867s
List related posts with vanilla related_posts	1.649s	4.899s
Preprocess, concatenate, minify, and cache bust SCSS and JS with jekyll-assets	78.751s	25.031s
Display masthead and overlay menu from _data	9.656s	7.815s
List post comments from _data	7.103s	2.216s
Display colophon from _data	0.2s	0.486s
List post taxonomy metadata	3.479s	1.182s
List post breadcrumb links	2.834s	1.029s
List featured posts	0.195s	0.439s
Build style guide collection	1.161s	0.314s
List post social sharing links	5.092s	0.973s

Worst case offenders appear to be resizing large amounts of images, copying images from source to destination, and building the site.

Decoupling asset generation tasks from main Jekyll build so they don't trigger a rebuild each time they are updated should help with development build times. Browsersync can also come to the rescue injecting updated CSS/JS to circumvent the entire Jekyll build process.

Jekyll build times comparison:

build type	Jekyll + plugins	Jekyll Gulpified
clean build (Mac OS)	26.01 min	14 min
clean build (Windows)	26.31 min	17 min
build with images already resized (Mac OS)	2.21 min	1.58 min
build with images already resized (Win)	5.23 min	4.17 min