Smaller "Difference from previous editions" chapter, one file per one version pair

docs/diff/README.md

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+---
+SPDX-License-Identifier: Community-Spec-1.0
+---
+
+# Differences between editions
+
+- [Differences between v3.0.1 and v3.0](./v3-0-0-v3-0-1.md)
+- [Differences between v3.0 and v2.3](./v2-3-0-v3-0-0.md)
+- [Differences between v2.3 and v2.2.2](./v2-2-2-v2-3-0.md)
+- [Differences between v2.2.2 and v2.2.1](./v2-2-1-v2-2-2.md)
+- [Differences between v2.2.1 and v2.2](./v2-2-0-v2-2-1.md)
+- [Differences between v2.2 and v2.1](./v2-1-0-v2-2-0.md)
+- [Differences between v2.1 and v2.0](./v2-0-0-v2-1-0.md)
+- [Differences between v2.0 and v1.2](./v1-2-0-v2-0-0.md)

docs/diff/v1-2-0-v2-0-0.md

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+---
+SPDX-License-Identifier: Community-Spec-1.0
+tags:
+  - v1.2
+  - v2.0
+---
+
+# Differences between V2.0 and V1.2
+
+- Abstraction has been applied to the underlying model with the inclusion of
+  SPDX elements. With SPDX 2.0, the concept of an SPDX element is introduced
+  (see Appendix III). This includes SPDX documents, SPDX files, and SPDX
+  packages, each of which gets associated with an SPDX identifier which is
+  denoted by “SPDXRef-”.
+
+- SPDX relationships have been added to allow any SPDX element to have a
+  relationship to other SPDX elements. Documented the origin of an SPDX
+  hierarchy of sub-packages, documenting the origin of an SPDX element, and
+  documenting modifications or corrections (annotations) to an SPDX element.
+
+- The ability to reference SPDX elements outside the current SPDX document
+  itself (external references).
+
+- Additional file types are now supported.
+
+- Additional checksum algorithms are now supported.
+
+- Review Information section is deprecated. It is recommended to provide
+  document reviews with Annotations (Section 7).
+
+- A License Expression Syntax has been introduced and documented in
+  Appendix IV.

docs/diff/v2-0-0-v2-1-0.md

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+---
+SPDX-License-Identifier: Community-Spec-1.0
+tags:
+  - v2.0
+  - v2.1
+---
+
+# Differences between V2.1 and V2.0
+
+- Snippets have been added to allow a portion of a file to be identified as
+  having different properties from the file it resides in.
+  The use of snippets is completely optional and it is not mandatory for
+  snippets to be identified. See section 5 Snippet Information for further
+  details on the fields available to describe snippets.
+
+- External Packages can now be referred to in SPDX documents.
+  When there is no SPDX file information available to document the content of
+  these external packages, then the filesAnalyzed attribute on a package should
+  be set to false. See section 3.8 Files Analyzed for more information.
+
+- Packages are now able to associate with an “External Reference” which allows
+  a Package to reference an external source of additional information,
+  metadata, enumerations, asset identifiers, or downloadable content believed
+  to be relevant to the Package.
+  See: section 3.21 External Reference, 3.22 External Reference Comment and
+  Appendix VI:  External Repository Identifiers for more information.
+
+- The “Artifact of Project” fields at the file level are now deprecated,
+  as they can be replaced by a relationship to the more descriptive
+  External Packages.
+
+- A new appendix “Using SPDX short identifiers in Source Files” has been added
+  to document the best practices to refer to the licenses in the SPDX license
+  list that have emerged from the development community.
+  See Appendix V: Using SPDX short identifiers in Source Files for more
+  information.
+
+- Miscellaneous bug fixes.

docs/diff/v2-1-0-v2-2-0.md

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+---
+SPDX-License-Identifier: Community-Spec-1.0
+tags:
+  - v2.1
+  - v2.2
+---
+
+# Differences from V2.2 and V2.1
+
+- JSON, YAML, and a development version of XML have been added as supported
+  file formats.
+
+- A new appendix "SPDX File Tags" has been added to describe a method that
+  developers can use to document other SPDX file-specific information
+  (such as copyright notices, file type, etc.) in a standardized and easily
+  machine-readable manner. See Appendix IX for more information.
+
+- A new appendix "SPDX Lite" has been added to document a lightweight subset of
+  the SPDX specification for scenarios where a full SPDX document is not
+  required. See Appendix VIII for more information.
+
+- Additional relationship options have been added to enable expression of
+  different forms of dependencies between SPDX elements. As well, NONE and
+  NOASSERTION keywords are now permitted to be used with relationships to
+  indicate what is unknown.
+
+- Miscellaneous bug fixes and non-breaking improvements as reported on the
+  mailing list and reported as issues on the spdx-spec GitHub repository.

docs/diff/v2-2-0-v2-2-1.md

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+---
+SPDX-License-Identifier: Community-Spec-1.0
+tags:
+  - v2.2
+  - v2.2.1
+---
+
+# Differences between V2.2.1 and V2.2
+
+There were no technical differences;
+V2.2.1 is V2.2 reformatted for submission to ISO via the PAS process.
+
+As a result, new clauses were added causing the previous clause-numbering
+sequence to change.
+Also, Annexes went from having Roman numbers to Latin letters.
+
+Here is the translation between numbering in V2.2.1
+and the version that came before it:
+
+**Table 1 — SPDX 2.2.1 Organizational Changes**
+
+| Title | V2.2 | V2.2.1 ([spdx.dev](https://spdx.dev/)) | V2.2.1 (ISO) |
+| ----- | ---- | -------------------------------------- | ------------ |
+| Scope                                             | N/A           | Clause 1   | Clause 1 |
+| Normative references                              | N/A           | Clause 2   | Clause 2 |
+| Terms and definitions                             | N/A           | Clause 3   | Clause 3 |
+| Conformance                                       | N/A           | Clause 4   | Clause 4 |
+| Composition of an SPDX document                   | N/A           | Clause 5   | Clause 5 |
+| Document Creation Information                     | Chapter 2     | Clause 6   | Clause 6 |
+| Package Information                               | Chapter 3     | Clause 7   | Clause 7 |
+| File Information                                  | Chapter 4     | Clause 8   | Clause 8 |
+| Snippet Information                               | Chapter 5     | Clause 9   | Clause 9 |
+| Other Licensing Information Detected              | Chapter 6     | Clause 10  | Clause 1 |
+| Relationship between SPDX Elements Information    | Chapter 7     | Clause 11  | Clause 1 |
+| Annotation Information                            | Chapter 8     | Clause 12  | Clause 1 |
+| Review Information (deprecated)                   | Chapter 9     | Clause 13  | Clause 1 |
+| SPDX License List                                 | Appendix I    | Annex A    | Annex A |
+| License Matching Guidelines and Templates         | Appendix II   | Annex B    | Annex B |
+| RDF Object Model and Identifier Syntax            | Appendix III  | Annex C    | Annex C |
+| SPDX License Expressions                          | Appendix IV   | Annex D    | Annex D |
+| Using SPDX short identifiers in Source Files      | Appendix V    | Annex E    | Annex E |
+| External Repository Identifiers                   | Appendix VI   | Annex F    | Annex F |
+| Creative Commons Attribution License 3.0 Unported | Appendix VII  | Annex G    | [omitted] |
+| SPDX Lite                                         | Appendix VIII | Annex H/G* | Annex G |
+| SPDX File Tags                                    | Appendix IX   | Annex I/H* | Annex H |
+| Differences from Earlier SPDX Versions            | N/A           | Annex J/I* | Annex I |
+
+**This edition featured inconsistent lettering.*

docs/diff/v2-2-1-v2-2-2.md

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+---
+SPDX-License-Identifier: Community-Spec-1.0
+tags:
+  - v2.2.1
+  - v2.2.2
+---
+
+# Differences between V2.2.2 and V2.2.1
+
+SPDX 2.2.2 fixed formatting, grammatical and spelling issues found
+since ISO/IEC 5962:2021 SPDX V2.2.1 was published.
+
+No new fields were added.
+
+Key changes include:
+
+- Clarify Optional Cardinality contradictions
+- Update OWL document
+- Update JSON schema to fix typos and add missing required fields.
+- Clarify Information on using License List short form identifiers.
+- It fixed annex lettering inconsistencies.
+  It also moved CC-BY-3.0 to the end of the spec to keep annex letters more
+  consistent in future versions.
+
+Here is the translation between lettering in V2.2.2
+and the version that came before it:
+
+**Table 1 — SPDX 2.2.2 Organizational Changes**
+
+| Title | V2.2.1 ([spdx.dev](https://spdx.dev/)) | V2.2.1 (ISO) | V2.2.2 |
+| ----- | -------------------------------------- | ------------ | ------ |
+| SPDX Lite                                         | Annex H/G* | Annex G   | Annex G |
+| SPDX File Tags                                    | Annex I/H* | Annex H   | Annex H |
+| Differences from Earlier SPDX Versions            | Annex J/I* | Annex I   | Annex I |
+| Creative Commons Attribution License 3.0 Unported | Annex G    | [omitted] | Annex J [omitted in ISO version] |
+
+**This edition featured inconsistent lettering.*

docs/diff/v2-2-2-v2-3-0.md

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+---
+SPDX-License-Identifier: Community-Spec-1.0
+tags:
+  - v2.2.2
+  - v2.3
+---
+
+# Differences between V2.3 and V2.2.2
+
+SPDX 2.3 has added new fields to improve the ability to capture security
+related information and to improve interoperability with other SBOM formats.
+
+Key changes include:
+
+- Added fields to Clause 7 ( Package Information ) to describe
+  "Primary Package Purpose" and standardize recording of "Built Date",
+  "Release Date", "Valid Until Date".
+
+- Added hash algorithms (SHA3-256, SHA3-384, SHA3-512, BLAKE2b-256,
+  BLAKE2b-384, BLAKE2b-512, BLAKE3, ADLER32 ) to the set recognized by 7.10
+  (Package Checksum field) and 8.4 (File checksum field)
+
+- Update Clause 7, 8, and 9 to make several of the licensing properties
+  optional rather than requiring the use of "NOASSERTION" when no value is
+  provided.
+
+- Update Clause 11 to add the new relationship types:
+  REQUIREMENT_DESCRIPTION_FOR and SPECIFICATION_FOR.
+
+- Update Annex B ( License matching guidelines and templates ) to use the
+  License List XML format
+
+- Update Annex F ( External Repository Identifiers ) to expand security
+  references to include advisory, fix, URL, SWID.
+  Expand persistent identifiers to include gitoid.
+
+- Update Annex G ( SPDX Lite Profile ) to include NTIA SBOM mandatory minimum
+  fields as required.
+
+- Update Annex H to documented how the snippet information in files to be
+  consistent with REUSE recommendations.
+
+- Added Annex K ( How To Use SPDX in Different Scenarios ) to illustrate
+  linking to external security information, and illustrate how the NTIA SBOM
+  mandatory minimum elements map to SPDX fields.