Speed up checkout by fetching minimal data from remote and lazily loading it later #612
Description
One of my big annoyances with the extension is how long it takes to checkout a branch, particularly on the first time checking this out. It's also even worse on Windows as git seems to be a little slower (due to FS?). This problem is also much worth with larger repos due to the size of the history, branch/tag count, etc.
I'm proposing that when a PR is checked out for the first time we fetch just the branch (r branch) and no history (--depth=1), something like this:
git remote add r
git fetch --depth 1 r branch
git checkout remote_branchThe history and rest of branches can then be lazily fetched later with this:
git fetch --unshallow rBased on my testing this should provide a very significant speed up:
Normal fetch and checkout:
powershell -Command "Measure-Command {git remote add r https://github.com/Tyriar/xterm.js; git fetch r}"
...
Days : 0
Hours : 0
Minutes : 0
Seconds : 2
Milliseconds : 935
Ticks : 29353111
TotalDays : 3.39735081018518E-05
TotalHours : 0.000815364194444444
TotalMinutes : 0.0489218516666667
TotalSeconds : 2.9353111
TotalMilliseconds : 2935.3111
Fetch remote branch only with no history:
powershell -Command "Measure-Command {git remote add r https://github.com/Tyriar/xterm.js; git fetch --depth 1 r 1747_npe}"
...
Days : 0
Hours : 0
Minutes : 0
Seconds : 1
Milliseconds : 149
Ticks : 11490152
TotalDays : 1.3298787037037E-05
TotalHours : 0.000319170888888889
TotalMinutes : 0.0191502533333333
TotalSeconds : 1.1490152
TotalMilliseconds : 1149.0152