remove obsolete doc about sha1 computation

superseded by the doc of swh.model.identifiers

README-dev.md

-Git sha1 computation
---------------------
-
-Document to describe how the git sha1 computation takes place.
-
-### commit/revision
-
-sha1 git commit/revision computation:
-
-    commit `size`\0
-    tree `sha1-git-tree-and-subtree-in-plain-hex-string`
-    ([parent `commit-parent-n`])
-    author `name` <`email`> `date-ts` `date-offset`
-    committer `name` <`email`> `date-ts` `date-offset`
-    ([extra-header-key-n extra-header-value-n])
-
-    `commit-message`
-    (inline-gpg-signature)
-
-
-Notes:
-- [] denotes list of entries (one per line)
-- () denotes optional entry. For example, the parent entry is optional.
-- empty line at the end of the commit message
-- timestamp example: 1444054085
-- date offset for example: +0200, -0100
-
-sources:
-- commit_tree_extended: https://github.com/git/git/blob/8d530c4d64ffcc853889f7b385f554d53db375ed/commit.c#L1522
-- commit_tree: https://github.com/git/git/blob/8d530c4d64ffcc853889f7b385f554d53db375ed/commit.c#L1392
-
-Examples:
-
-```sh
-$ cat commit.txt
-tree 85a74718d377195e1efd0843ba4f3260bad4fe07
-parent 01e2d0627a9a6edb24c37db45db5ecb31e9de808
-author Linus Torvalds <torvalds@linux-foundation.org> 1436739030 -0700
-committer Linus Torvalds <torvalds@linux-foundation.org> 1436739030 -0700
-svn-repo-uuid 046f1af7-66c2-d61b-5410-ce57b7db7bff
-svn-revision 10
-
-Linux 4.2-rc2
-```
-
-```
-$ cat commit.txt | git hash-object -t commit --stdin
-010d34f384fa99d047cdd5e2f41e56e5c2feee45
-```
-
-commit: 44cc742a8ca17b9c279be4cc195a93a6ef7a320e
-```
-$ git cat-file -p 44cc742a8ca17b9c279be4cc195a93a6ef7a320e
-...
-tree b134f9b7dc434f593c0bab696345548b37de0558
-parent 689664ae944b4692724f13b709a4e4de28b54e57
-parent c888305e1efbaa252d01b4e5e6b778f865a97514
-author Jiang Xin <worldhello.net@gmail.com> 1428538899 +0800
-committer Jiang Xin <worldhello.net@gmail.com> 1428538899 +0800
-gpgsig -----BEGIN PGP SIGNATURE-----
- Version: GnuPG v1.4.13 (Darwin)
-
- iQIcBAABAgAGBQJVJcYsAAoJEBiY3kIkQRNJVAUQAJ8/XQIfMqqC5oYeEFfHOPYZ
- L7qy46bXHVBa9Qd8zAJ2Dou3IbI2ZoF6/Et89K/UggOycMlt5FKV/9toWyuZv4Po
- L682wonoxX99qvVTHo6+wtnmYO7+G0f82h+qHMErxjP+I6gzRNBvRr+SfY7VlGdK
- wikMKOMWC5smrScSHITnOq1Ews5pe3N7qDYMzK0XVZmgDoaem4RSWMJs4My/qVLN
- e0CqYWq2A22GX7sXl6pjneJYQvcAXUX+CAzp24QnPSb+Q22Guj91TcxLFcHCTDdn
- qgqMsEyMiisoglwrCbO+D+1xq9mjN9tNFWP66SQ48mrrHYTBV5sz9eJyDfroJaLP
- CWgbDTgq6GzRMehHT3hXfYS5NNatjnhkNISXR7pnVP/obIi/vpWh5ll6Gd8q26z+
- a/O41UzOaLTeNI365MWT4/cnXohVLRG7iVJbAbCxoQmEgsYMRc/pBAzWJtLfcB2G
- jdTswYL6+MUdL8sB9pZ82D+BP/YAdHe69CyTu1lk9RT2pYtI/kkfjHubXBCYEJSG
- +VGllBbYG6idQJpyrOYNRJyrDi9yvDJ2W+S0iQrlZrxzGBVGTB/y65S8C+2WTBcE
- lf1Qb5GDsQrZWgD+jtWTywOYHtCBwyCKSAXxSARMbNPeak9WPlcW/Jmu+fUcMe2x
- dg1KdHOa34shrKDaOVzW
- =od6m
- -----END PGP SIGNATURE-----
-
-Merge branch 'master' of git://github.com/alexhenrie/git-po
-
-* 'master' of git://github.com/alexhenrie/git-po:
-  l10n: ca.po: update translation
-```
-
-### directory/tree
-
-sha1 git directory/tree computation:
-
-    tree `tree-size`\0
-    <file-perm> <file-name>\0<file-sha1-in-20-bytes-string>...<dir-perm> <dir-name>\0<dir-sha1-in-20-bytes-string>...
-
-
-Notes:
-- no newline separator between tree entries
-- no empty newline at the end of the tree entries
-- tree content header size is the length of the content
-- The tree entries are ordered according to bytes in their <name> properties.
-
-Note: Tree entries referencing trees are sorted as if their name have a trailing /
-at their end.
-
-Possible permissions are:
-- 100644 - file
-- 40000  - directory
-- 100755 - executable file
-- 120000 - symbolink link
-- 160000 - git link (relative to submodule)
-
-### content/file
-
-sha1 git content computation:
-
-    blob `blob-size`\0
-    `blob-content`
-
-Notes:
-- no newline at the end of the blob content
-
-Compress with DEFLATE and compute sha1