Using ssh protocol for submodule pulls

[oddhack]

In a comment on #1180 (comment), there's a suggestion to configure the submodules of this repo to pull via ssh instead of https protocol. I tried this out in a repo fork (https://github.com/oddhack/Vulkan-Samples) and it does seem more reliable. Download performance is about halved, ca. 15-30 MB/s instead of the 20-50 MB/s I get over https when it's working, which is a drawback (maybe just particular to my machine, which is an aging Ryzen 2600?)

The main drawback appears to be that using ssh protocol requires configuring a github ssh key setup (AFAICT). This is a no-op for me since I always use ssh to github, but it could impose a transition cost or unacceptable restriction on some repo users.

Unfortunately, there doesn't (seem) to be any way to configure this on a connection basis, e.g. clone the submodules using the same protocol as Vulkan-Samples itself. Again AFAICT, the protocol selection is controlled by .gitmodules in the default repository branch, and you don't have access to the default repository branch when performing a 'git clone --recurse-submodules' until after the entire operation is finished. The multi-step procedure outlined in the comment is workable but is not nearly as simple as the --recurse-submodules variant:

git clone git@github.com:KhronosGroup/Vulkan-Samples.git
cd Vulkan-Samples
perl -i -p -e 's|https://(.*?)/|git@\1:|g' .gitmodules
git submodule sync
git submodule update

Possibly we could add this to the recent NOTE from #1194 as a workaround? I could also implement it in the Vulkan-Site repository setup target.

[SaschaWillems]

Kinda torn on this. Aside from the fact that SSH is usually slower (which is kinda critical as our repo incl. assets is large), SSH might be blocked for people, esp. behind corporate firewalls. So having this as default might cause more trouble than living with the isolated https issues.

[oddhack]

#1216 added the ssh workaround to the README, for those who need it. Closing this.