Speed up migration squasher

What does this MR do and why?

This speeds up the migration squasher (rake gitlab:db:squash) by skipping to pass files that don’t exist to 'git rm'.

On my laptop, the task takes about 265s before the change, which drops down to about 38.033s ± 0.658s after the change. I didn’t measure a full hyperfine run because it would've taken over half an hour. About a 86% drop should be significant enough though.

MR acceptance checklist

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How to set up and validate locally

1. Run bundle exec rake gitlab:db:squash\[origin/16-3-stable-ee\]
2. See that it finishes in less than half a minute

added Engineering Productivity database maintenancerefactor labels

assigned to @kkloss

added typemaintenance label

added pipelinetier-1 label

added backend databasereview pending labels

	1 Warning
	The master pipeline status page reported failures in rspec system pg14 26/32 rspec integration pg14 5/20 If these jobs fail in your merge request with the same errors, then they are not caused by your changes. Please check for any on-going incidents in the incident issue tracker or in the #master-broken Slack channel.

	1 Message
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Reviewer roulette

Category	Reviewer	Maintainer
backend	@ahegyi (UTC+2, same timezone as author)	@maddievn (UTC+2, same timezone as author)
database	@johnmason (UTC-4, 6 hours behind author)	@ahegyi (UTC+2, same timezone as author)

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Generated by Danger

changed milestone to %17.5

@OmarQunsulGitlab, could you please review this small MR?

requested review from @OmarQunsulGitlab

mentioned in issue gitlab-org/quality/engineering-productivity/team#564 (closed)

approved this merge request

added pipeline:mr-approved label

added databasereviewed label and removed databasereview pending label

added pipelinetier-2 label and removed pipelinetier-1 label

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E2E Test Result Summary

allure-report-publisher generated test report!

e2e-test-on-gdk: test report for d9bd3cdc

expand test summary

+------------------------------------------------------------------+
|                          suites summary                          |
+-------------+--------+--------+---------+-------+-------+--------+
|             | passed | failed | skipped | flaky | total | result |
+-------------+--------+--------+---------+-------+-------+--------+
| Verify      | 45     | 0      | 2       | 0     | 47    | ✅     |
| Secure      | 4      | 0      | 0       | 0     | 4     | ✅     |
| Create      | 128    | 0      | 18      | 0     | 146   | ✅     |
| Data Stores | 33     | 0      | 1       | 0     | 34    | ✅     |
| Package     | 24     | 0      | 11      | 0     | 35    | ✅     |
| Plan        | 76     | 0      | 0       | 1     | 76    | ✅     |
| Govern      | 73     | 0      | 0       | 0     | 73    | ✅     |
| Manage      | 1      | 0      | 1       | 0     | 2     | ✅     |
| Fulfillment | 2      | 0      | 0       | 0     | 2     | ✅     |
| Analytics   | 2      | 0      | 0       | 0     | 2     | ✅     |
| Monitor     | 8      | 0      | 0       | 0     | 8     | ✅     |
| Release     | 5      | 0      | 0       | 0     | 5     | ✅     |
+-------------+--------+--------+---------+-------+-------+--------+
| Total       | 401    | 0      | 33      | 1     | 434   | ✅     |
+-------------+--------+--------+---------+-------+-------+--------+

added 1 commit

• d9bd3cdc - Speed up migration squasher

Compare with previous version

note: turns out, git.remove accepts an array, which would make this more than 10x times faster than the previous version (265s to 16s). I pushed the change.

kev@MBPsomtllhorKev gitlab % hyperfine -p 'git reset && git checkout db' 'bundle exec rake "gitlab:db:squash[origin/16-3-stable-ee]"'                                                                 
Benchmark 1: bundle exec rake "gitlab:db:squash[origin/16-3-stable-ee]"
  Time (mean ± σ):     16.243 s ±  1.433 s    [User: 6.246 s, System: 4.336 s]
  Range (min … max):   12.812 s … 18.277 s    10 runs

@morefice, could you take a look again, please?

requested review from @morefice

changed the description