Doc Fix for Alembic multiple heads error

Add documentation to fix multiple heads Alembic error. Create file
contributor/troubleshooting.rst and update contributor/index.rst.

Closes-Bug: 1548371

Change-Id: I957bf1c7529f9409d8026f43d5fa8e04b9278d61
This commit is contained in:
Kirsten G 2017-10-23 13:11:50 -07:00 committed by Kirsten
parent 2164b26df5
commit 7482e65a2d
2 changed files with 32 additions and 0 deletions

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@ -14,6 +14,7 @@ project.
Developer Contribution Guide <contributing>
Setting Up Your Development Environment <quickstart>
Running Tempest Tests <functional-test>
Developer Troubleshooting Guide <troubleshooting>
There are some other important documents also that helps new contributors to
contribute effectively towards code standards to the project.

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Developer Troubleshooting Guide
================================
This guide is intended to provide information on how to resolve common
problems encountered when developing code for magnum.
Troubleshooting MySQL
-----------------------
When creating alembic migrations, developers might encounter the ``Multiple
head revisions are present for given argument 'head'`` error.
This can occur when two migrations revise the same head. For example, the
developer creates a migration locally but another migration has already been
accepted and merged into master that revises the same head::
$ alembic heads
12345 (your local head)
67890 (new master head)
In order to fix this, the developer should update the down_revision of their
local migration to point to the head of the new migration in master::
# revision identifiers, used by Alembic.
revision = '12345'
down_revision = '67890'
Now the newest local migration should be head::
$ alembic heads
12345 (your local head)