CRM-21787 : Simplify CRM_Utils_System::version() to fetch version directly from xml/version.xml

[monishdeb]

Overview

This patch simplifies CRM_Utils_System::version() by removing a level of indirection -- instead of reading xml/version.xml indirectly (by way of civicrm-version.php and GenCode), it reads xml/version.xml directly.

This change is valid now that xml/version.xml is included with tarballs (04e5df1).

Before

CRM_Utils_System::version() reads civicrm-version.php OR xml/version.xml.

After

CRM_Utils_System::version() reads xml/version.xml.

Technical Details

To avoid CRM_Core_CodeGen_Version dependency to generate civicrm-version.php is to make this file independent, to retrieve the cms and version on its own. For version, it's possible to directly use xml/version.xml but for cms we need to rely on php constant CIVICRM_UF. Then we can easily remove CRM_Core_CodeGen_Version. (Outside scope of this PR.)

Comments

This PR contains commits of #11695

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• CRM-21787: Keep civicrm-version.php up-to-date without running GenCode on all builds

[monishdeb]

ping @totten

[totten]

@monishdeb I updated the description to simplify the prose and remove the comments about cms/CIVICRM_UF. Why? Because (a) this patch (e48985c) focuses on CRM_Utils_System::version() which never cared about the cms or CIVICRM_UF, and (b) if we were talking about civicrm-version.php, CIVICRM_UF wouldn't be a substitute for cms. (But we can talk about that more in an issue or PR that focuses on civicrm-version.php.)

[monishdeb]

Yeah agree with the edit, which was not appropriate to drag the topic of making civicrm-version.php sel-sufficient, in this PR.