[Command::Update] Update docs for --sources

Fix cross-project framework dependencies

Fix whitespace in changelog

Update Issue Template

[update] adding --sources to specify to only update pods from a repo

[Command] Raise when using git < 1.8.5

[Embed] Fix codesigning issues when targets have spaces

Fix for lint codesign failure on macOS projects

This small change fixes an issue with `{target}-frameworks.sh`, wherein spaces in the target cause a `No such file or directory` error. The fix is simple: wrap `code_sign_if_enabled` in quotes. Works in my local env and hope it works in yours too 👍

Fixes and closes CocoaPods/CocoaPods#6153.

Bump the master submodule to a post-sharding commit

[SourcesManager] Remove const_missing hack

It's been months, time for this hack to go

[Spec::Lint] Fail gracefully when downloading podspec fails