If the library/component is wide spread, it either can be developed in a branch, and specific version be tagged, or always developed "trunk" mode with feature t

If the library/component is wide spread, it either can be developed in a branch, and specific version be tagged, or always developed "trunk" mode with feature toggles (may not be always possible, but one can adjust), e.g. - certain features are disabled, and need to be enabled after others come across, or after some specific time, etc. While at google, we used that kind of development for the project I was in. Someone would push source code changes for new features, but prefferable behind a flag (normally a command-line flag, driven to a configuration, like the one ksonnet has). The confiuration file would say - enable this flag, only the binary was compiled with this CL version, and/or these cherrypicks, or some other rule. This also allows a feature to be quickly disabled by SRE, SWE, or other personnel if it's found to be not working well.