[Packaging] restore php.ini if something bad happened

[v1v]

What

Let's restore the php.ini file if something bad happened. The restore should keep the file as used to be and also preserving the permissions.

Tests

$ rm -rf build
$ PHP_VERSION=7.4 make -f .ci/Makefile build
$ PHP_VERSION=7.4 make -C packaging rpm

Then, it will fail if installing php.7.4 in in php7.2:

$ PHP_VERSION=7.2 make -C packaging rpm-install
...

Installing Elastic PHP agent
; THIS IS AN AUTO-GENERATED FILE by the Elastic PHP agent post-install.sh script
extension=/opt/elastic/apm-agent-php/extensions/elastic_apm.so
elastic_apm.bootstrap_php_part_file=/opt/elastic/apm-agent-php/src/bootstrap_php_part.php
; END OF AUTO-GENERATED
PHP Warning:  PHP Startup: Unable to load dynamic library '/opt/elastic/apm-agent-php/extensions/elastic_apm.so' (tried: /opt/elastic/apm-agent-php/extensions/elastic_apm.so (/opt/elastic/apm-agent-php/extensions/elastic_apm.so: undefined symbol: zend_hash_add), /usr/lib64/php/modules//opt/elastic/apm-agent-php/extensions/elastic_apm.so.so (/usr/lib64/php/modules//opt/elastic/apm-agent-php/extensions/elastic_apm.so.so: cannot open shared object file: No such file or directory)) in Unknown on line 0
Failed enabling Elastic PHP agent extension
Reverted changes in the file /etc/php.ini
Set up the Agent manually as explained in:
https://github.com/elastic/apm-agent-php/blob/master/docs/setup.asciidoc

Then it will work when installing it in a php.version 7.4

$ PHP_VERSION=7.4 make -C packaging rpm-install
Installing Elastic PHP agent
; THIS IS AN AUTO-GENERATED FILE by the Elastic PHP agent post-install.sh script
extension=/opt/elastic/apm-agent-php/extensions/elastic_apm.so
elastic_apm.bootstrap_php_part_file=/opt/elastic/apm-agent-php/src/bootstrap_php_part.php
; END OF AUTO-GENERATED
Extension enabled successfully for Elastic PHP agent
+ php -m
+ grep -q elastic
+ composer install
Loading composer repositories with package information
Updating dependencies (including require-dev)

Issues

Closes #112

[v1v]

For the record, it uses the -f flag, so it forces the move, are we happy with this approach?

[v1v]

-fa flag should help to force if the file already exists and then it will populate the permissions too. Are we happy with this approach?

[SergeyKleyman]

So after restore will the file have the same owner user/group and permissions?

[v1v]

IIUC, that's the meaning for those flags, see below:

     -a    Same as -pPR options. Preserves structure and attributes of files but not directory structure.

     -f    If the destination file cannot be opened, remove it and create a new file, without prompting for confirmation regardless of its permissions.  (The -f option overrides any
           previous -n option.)

           The target file is not unlinked before the copy.  Thus, any existing access rights will be retained.
     -p    Cause cp to preserve the following attributes of each source file in the copy: modification time, access time, file flags, file mode, user ID, and group ID, as allowed by
           permissions.  Access Control Lists (ACLs) and Extended Attributes (EAs), including resource forks, will also be preserved.

           If the user ID and group ID cannot be preserved, no error message is displayed and the exit value is not altered.

           If the source file has its set-user-ID bit on and the user ID cannot be preserved, the set-user-ID bit is not preserved in the copy's permissions.  If the source file has
           its set-group-ID bit on and the group ID cannot be preserved, the set-group-ID bit is not preserved in the copy's permissions.  If the source file has both its set-user-ID
           and set-group-ID bits on, and either the user ID or group ID cannot be preserved, neither the set-user-ID nor set-group-ID bits are preserved in the copy's permissions.

[apmmachine]

💚 Build Succeeded

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Build stats

• Build Cause: [Pull request #116 updated]

• Start Time: 2020-08-06T13:31:35.304+0000

• Duration: 9 min 56 sec

Test stats 🧪

Test	Results
Failed	0
Passed	108
Skipped	0
Total	108