update CONTRIBUTING

CONTRIBUTING.md

@@ -5,19 +5,23 @@
 
 A collaborative database design project poses challenges when it comes to version-control and collaborative development. Developers must take care to make sure their development databases are up to date, for example. 
 
-This repository has two concurrent branches to avoid confusion for new users. `master` is meant for new users looking for a complete new installation. `master/sql` contains only two files, one to make a new DB and one to make a complete installation (we call this "onebigfile.sql"). Onebigfiles are dumps of the database
+This repository has two concurrent branches to avoid confusion for new users. `master` is meant for new users looking for a complete new installation. `master/sql` contains only two files, one to make a new DB and one to make a complete installation (we call this "onebigfile.sql" or OBF). Onebigfiles are dumps of the database
 
-`migration` contains incremental changes to existing installations. 
+`migration` contains incremental changes ("patches") to existing installations. Executing all the patches in sequence on an empty database should, in theory, produce a database identical to one made from an up-to-date onebigfile. Exceptions are these situations:
+
+- Patches have been written, but are not yet committed into the latest version of OBF. We try to disambiguate OBF versions by appending the latest patch committed to it, e.g. OBF33 would have the 33_ patch in it. 
+- Some patches are sequentially numbered, but are optional and are not committed to OBF. "Delete" scripts to delete example data, etc.
+- We goofed up somewhere. 
 
 ### Step-by-step guide
 
 You might want to git CHECK OUT the two branches `master` and `migration` in different directories.
 
-ALWAYS follow these steps at the beginning of a coding session.
+ALWAYS follow these steps at the beginning of a coding session. It looks scary, but should be intuitive once you're used to the workflow.
 
 1. Make sure the `master` branch is checked out.
-1. Obtain the patch number incorporated into the current onebigfile. This might be recorded in the latest commit message to `onebigfile.sql`. For example, onebigfile 24 would contain all patches from 1-24. 
-1. Edit the GRANT statements in `onebigfile.sql`. For development purposes, we recommend making two users named `read_write_user` and `read_only_user` in your Postgres installation. Then find-and-replace all occurrences of `%db_owner%` with the role you are using. DO NOT COMMIT this edited file. `Save as` a local copy. For example,
+2. Obtain the patch number incorporated into the current onebigfile. This might be recorded in the latest commit message to `onebigfile.sql`. For example, onebigfile 24 would contain all patches from 1-24. 
+3. Edit the GRANT statements in `onebigfile.sql`. For development purposes, we recommend making two users named `read_write_user` and `read_only_user` in your Postgres installation. Then find-and-replace all occurrences of `%db_owner%` with the role you are using. DO NOT COMMIT this edited file. `Save as` a local copy. For example,
 ```
 cat onebigfile.sql | sed 's/%db_owner%/your_username/g' > local_temporary_onebigfile.sql
 ```
@@ -34,8 +38,8 @@ INSERT INTO pkg_mgmt.version_tracker_metabase
 VALUES(0, 9, 22, now(), 'applied 22_version_tracker');
 ```
 8. Once testing is done, make a new file and put in the exact SQL needed to make the changes you want. Name this file in this pattern: (the next integer up from the onebigfile patch number)-(underscore)-(brief description of what this patch does). For example, if you installed OBF 24 and created a new table to model the quality control EML tree, name your patch "25_create_quality_control_tables.sql". 
-1. Commit this patch to the `sql` folder in the `migration` branch. 
-1. Make a dump of your test DB, complete with changes and new row in version tracker. An example `pg_dump` command would be: 
+9. Commit this patch to the `sql` folder in the `migration` branch. 
+10. Make a dump of your test DB, complete with changes and new row in version tracker. An example `pg_dump` command would be: 
 ```
 pg_dump -d <DB name> -F p -b -h your_db_host -p 5432 -U your_username -f <file path to dump to>
 ```
@@ -46,8 +50,8 @@ cat pg_dump_output.sql | sed 's/your_username/%db_owner%/g' > onebigfile.sql
 12. If you created any new tables or views, make sure `read_write_user` is granted SELECT, UPDATE, INSERT to all tables, `read_only_user` only SELECT.
 Rename the dump to `onebigfile.sql` and commit it to the master branch in the `sql` folder. Make sure to include your patch number in the commit message.
 
-1. If you have doubt you have captured the end state of the db, the most safe process is to install the previous onebigfile again, apply the patch file, dump, and diff the two dumps. That is not usually necessary. 
-1. Note the onebigfile.sql must be made using pg_dump from the same version of postgres to be comparable to past and future onebigfile commits. As of July 2019 we are using postgres 11 for this. 
+13. If you have doubt you have captured the end state of the db, the most safe process is to install the previous onebigfile again, apply the patch file, dump, and diff the two dumps. That is not usually necessary. 
+14. Note the onebigfile.sql must be made using pg_dump from the same version of postgres to be comparable to past and future onebigfile commits. As of July 2019 we are using postgres 11 for this. 
 
 ## Revisions