chore: import upstream snapshot with attribution

dockerREADME.md

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+# Doltgres is Dolt for Postgres!
+
+From the creators of [Dolt](https://www.doltdb.com), the world's first version-controlled SQL
+database, comes [Doltgres](https://www.doltgres.com), the Postgres-flavored version of Dolt. It's a
+SQL database that you can branch and merge, fork and clone, push and pull, just like a Git
+repository. Connect to your Doltgres server just like any Postgres database to read or modify schema
+and data. Version control functionality is exposed in SQL via system tables, functions, and
+procedures.
+
+Git versions file, Doltgres versions tables. It's like Git and Postgres had a baby.
+
+[Join us on Discord](https://discord.com/invite/RFwfYpu) to say hi and
+ask questions, or [check out our roadmap](https://dolthub.com/docs/other/roadmap)
+to see what we're building next.
+
+## What's it for?
+
+Lots of things! Doltgres is a generally useful tool with countless applications. But if you want
+some ideas, [here's how people are using it so
+far](https://www.dolthub.com/blog/2022-07-11-dolt-case-studies/).
+
+# How to use this image
+
+This image is for the Doltgres server and is similar to the Postgres Docker image. Running this
+image without any arguments is equivalent to running the `doltgres` command inside a Docker
+container.
+
+To see all supported options for `doltgres`, you can run the image with `--help` flag.
+
+```shell
+$ docker run dolthub/doltgresql:latest --help
+```
+
+## Building the image
+
+To build this image, use the `Dockerfile` in the root of the [Doltgres
+repository](https://github.com/dolthub/doltgresql/) with an optional build argument:
+
+```shell
+# Build the latest Doltgres version (automatically fetches the latest release)
+$ docker build -t doltgres:latest .
+
+# Build the latest Doltgres version (fetches the latest release)
+$ docker build --build-arg DOLTGRES_VERSION=latest -t doltgres:latest .
+
+# Build with a specific Doltgres version
+$ docker build --build-arg DOLTGRES_VERSION=0.55.1 -t doltgres:0.55.1 .
+
+# Build from local source code
+$ docker build --build-arg DOLTGRES_VERSION=source -t doltgres:source .
+```
+
+## Connect to the server in the container from the host system
+
+To connect to a server running in a container from the host system, we need to map a port on the
+host system to the port our server is running on in the container.
+
+```bash
+$ docker run -p 5432:5432 dolthub/doltgresql:latest
+```
+
+*Note*: if you have Postgres installed on this machine already, port `5432` will be in use. Either
+choose a different port to map or shut down Postgres.
+
+Now connect with `psql` or another Postgres-compatible client.
+
+```bash
+$ PGPASSWORD=password psql --host 127.0.0.1 -U postgres
+```
+
+## Define configuration for the server
+
+You can specify server configuration by providing your own `config.yaml` for the server to use as a
+mounted volume. The image looks for a `config.yaml` file in the mounted directory
+`/etc/doltgres/servercfg.d`. Place your desired `config.yaml` directory in a local file, then
+provide it to `docker run` with the `-v` argument like this:
+
+```shell
+$ docker run -v ./doltgres_cfg:/etc/doltgres/servercfg.d -p 5432:5432 dolthub/doltgresql:latest
+```
+
+The data directory in the container is `/var/lib/doltgresql/`. To change this, provide the `PGDATA`
+or `DOLTGRES_DATA` environment variable to `docker run`. This directory can also be a mounted
+directory on the local machine.
+
+```shell
+$ docker run -e PGDATA=/path/to/doltgres/data -p 5432:5432 dolthub/doltgresql:latest
+```
+
+## Specifying a username and password
+
+By default, the server creates a super-user named `postgres` with the password `password`. To change
+this, provide the `DOLTGRES_USER` and `DOLTGRES_PASSWORD` environment variables to the `docker run`
+command.
+
+```shell
+$ docker run -e DOLTGRES_USER=myuser -e DOLTGRES_PASSWORD=mypass -p 5432:5432 dolthub/doltgresql:latest
+```
+
+For convenience, `POSTGRES_USER` and `POSTGRES_PASSWORD` are accepted as aliases for these variables.
+
+To create additional users, connect to the running database and issue `CREATE ROLE` and `GRANT`
+statements as the super-user.
+
+## Initialization
+
+By default, the Doltgres server is initialized with a single empty database with the same name as
+the system user (`postgres` by default). You can add additional data or execute arbitrary SQL setup
+by including initialization scripts in the mounted volume
+`/docker-entrypoint-initdb.d/`. Initialization scripts must have the `.sql` file extension and
+contain statements separated by semicolons. They can be optionally compressed as `.bz2`, `.gz`,
+`.xz`, or `.zst` files with the appropriate extension suffix, e.g. `init.sql.gz`.
+
+Specify an initialization script directory as a volume with `docker run`:
+
+```shell
+$ docker run -v ./init_scripts:/docker-entrypoint-initdb.d/ -p 5432:5432 dolthub/doltgresql:latest
+```
+
+## Environment Variables
+
+The Doltgres image supports the following environment variables:
+
+- `DOLTGRES_USER`: The name of the super-user (default: `postgres`). `POSTGRES_USER` is an alias.
+- `DOLTGRES_PASSWORD`: The password for the super-user (default: `password`). `POSTGRES_PASSWORD` is
+  an alias.
+- `DOLTGRES_DATA`: Specifies a path in the container to store database data, created if it doesn't
+  exist (default: `/var/lib/doltgresql/`). `PGDATA` is an alias.