Add http support for git repository context

[yw-liu]

Description

In developing or testing environment, add http support for Git Repository context would be helpful.

Usage: set the GIT_PULL_METHOD env var to http or https when starting the container.

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[googlebot]

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[tejal29]

Suggested change

	gitPullMethod = gitPullMethodHTTPS
	return gitPullMethodHTTPS

[yw-liu]

Thanks @tejal29 for your suggestion, you may commit that.

[tejal29]

Thanks @yw-liu for your PR.