Add reporting entrypoint file and its tests, and link it to main

[victoria-miltcheva]

Related issue

Supports internal issue 623 in Team-backlog

Description of changes

This is a sub-PR of https://github.com/IBM/detect-secrets/pull/46 (I'm breaking down the reporting PR for easier readability for reviewers).

• Adds report.py, which serves as the entrypoint for the audit reporting functionality.
• Adds report.py execute function to main.py, so reporting can now be used.
• Adds tests for reporting
• usage.py: moves filename argument to end, updates usage string to be more readable.

[victoria-miltcheva]

To test the reporting functionality directly, create a test.py file in the root of detect-secrets, and run it with python test.py.

Example contents (uncomment sections to test, you'll also need to edit values in your secrets (see https://github.com/victoria-miltcheva/detect-secrets/blob/reporting-pr-8/detect_secrets/core/report/conditions.py) to cause conditions to fail):

import detect_secrets.main

# provide cli args as an array here
# detect_secrets.main.main(['audit', '.secrets.baseline'])

### Error cases ###

# Case --fail-on-live
# detect_secrets.main.main(["audit", "--fail-on-live", ".secrets.baseline",])

# Case --fail-on-audited-real
# detect_secrets.main.main(["audit", "--fail-on-audited-real"], ".secrets.baseline", )

# Case --fail-on-unaudited
# detect_secrets.main.main(["audit", "--fail-on-unaudited", ".secrets.baseline", ])

# Case --omit-instructions
# detect_secrets.main.main(["audit", "--omit-instructions", ".secrets.baseline"])

# Case --json
# detect_secrets.main.main(["audit", "--json", ".secrets.baseline",])

# Case: json with omit instructions, error
# detect_secrets.main.main(["audit", "--report", "--json", "--omit-instructions"])

### Help ###

# Case: audit report help
# detect_secrets.main.main(["audit", "--report", "--help"])

### Reporting ###

# Case: report only
# detect_secrets.main.main(["audit", "--report", ".secrets.baseline"])

# Case: all fail args and default report
# detect_secrets.main.main(
#     [
#         "audit",
#         "--report",
#         "--fail-on-unaudited",
#         "--fail-on-live",
#         "--fail-on-audited-real",
#         ".secrets.baseline",
#     ]
# )

# # Case: omit instructions
# detect_secrets.main.main(
#     [
#         "audit",
#         "--report",
#         "--fail-on-unaudited",
#         "--fail-on-live",
#         "--fail-on-audited-real",
#         "--omit-instructions",
#         ".secrets.baseline",
#     ]
# )

# Case: JSON
# detect_secrets.main.main(
#     [
#         "audit",
#         "--report",
#         "--fail-on-unaudited",
#         "--fail-on-live",
#         "--fail-on-audited-real",
#         "--json",
#         ".secrets.baseline",
#     ]
# )

# Case: fail on unaudited
# detect_secrets.main.main(["audit", "--report", "--fail-on-unaudited", ".secrets.baseline",])

# Case: fail on live only
# detect_secrets.main.main(["audit", "--report", "--fail-on-live", ".secrets.baseline",])

# Case: fail on audited real only
# detect_secrets.main.main(["audit", "--report", "--fail-on-audited-real, ".secrets.baseline","])