Allow `BBOX` to be set in `.env` file (#1013)

* Allow setting `BBOX` to be set in `.env` file

Currently, the `BBOX` setting in `.env` is ignored for all areas except `planet`.
On the other hand, the `planet` area is an overkill for any `BBOX` setting other than the default - `-180.0,-85.0511,180.0,85.0511`.

With this PR, `quickstart.sh` would not override a modified `BBOX` value in `.env`. 

Also, this provides a way to avoid the pessimistic `BBOX` computation for `osmfr` extracts, as described in https://github.com/openmaptiles/openmaptiles-tools/pull/297#issuecomment-700792702

#### Currently
- If the user does not do anything, `quickstart.sh` and `make generate-tiles` create an `mbtiles` file for the full extent of the data source. This applies to `planet` and other data sources.
- If a user sets the `BBOX` value in `.env` and a `planet` data source is used, `quickstart.sh` and `make generate-tiles` create an `mbtiles` file for the extent set in the `.env` file.
- If a user sets the `BBOX` value in `.env` and a non-`planet` data source is used, it is ignored - `quickstart.sh` and `make generate-tiles` create an `mbtiles` file for the full extent of the data source.

#### Problem statement
While users of a `planet` data source have a simple way to override the default extend of the tile generation, users of other data sources have no simple way of doing that. In fact, for such users the `BBOX` setting in the `.env` file is ignored and therefore misleading.

#### Proposal
- If the user does not do anything, `quickstart.sh` and `make generate-tiles` create an `mbtiles` file for the full extent of the data source. This applies to `planet` and other data sources.
- If a user sets the `BBOX` value in `.env`, `quickstart.sh` and `make generate-tiles` create an `mbtiles` file for the extent set in the `.env` file. This applies to `planet` and other data sources.

.env

@@ -13,8 +13,8 @@ PGPASSWORD=openmaptiles
 PGHOST=postgres
 PGPORT=5432
 
-# BBOX may get overwritten by the computed bbox of the specific area:
-#   make generate-dc-config
+# By default, tile generation is done for the full extent of the given area.
+# Modify BBOX below to overwrite it.
 BBOX=-180.0,-85.0511,180.0,85.0511
 
 # Which zooms to generate in   make generate-tiles

QUICKSTART.md

@@ -397,6 +397,17 @@ Hints:
 * Small increments! Never starts with the `MAX_ZOOM = 14`
 * The suggested  `MAX_ZOOM = 14`  - use only with small extracts
 
+### Set the bounding box to generate
+
+By default, tile generation is done for the full extent of the area.
+If you want to generate a tiles for a smaller extent, modify the settings in the `.env` file, the default:
+* `BBOX=-180.0,-85.0511,180.0,85.0511`
+
+Delete the `./data/<area>.dc-config.yml` file, and re-start `./quickstart.sh <area>`
+
+Hint:
+* The [boundingbox.klokantech.com](https://boundingbox.klokantech.com/) site can be used to find a bounding box (CSV format) using a map.
+
 ### Check other commands
 
 `make help`

quickstart.sh

@@ -263,11 +263,15 @@ make test-perf-null
 
 echo " "
 echo "-------------------------------------------------------------------------------------"
-if [[ "$area" != "planet" ]]; then
-  echo "====> : Compute bounding box for tile generation"
-  make generate-dc-config ${MIN_ZOOM:+MIN_ZOOM="${MIN_ZOOM}"} ${MAX_ZOOM:+MAX_ZOOM="${MAX_ZOOM}"}
+if [[ "$(source .env ; echo "$BBOX")" = "-180.0,-85.0511,180.0,85.0511" ]]; then
+  if [[ "$area" != "planet" ]]; then
+    echo "====> : Compute bounding box for tile generation"
+    make generate-dc-config ${MIN_ZOOM:+MIN_ZOOM="${MIN_ZOOM}"} ${MAX_ZOOM:+MAX_ZOOM="${MAX_ZOOM}"}
+  else
+    echo "====> : Skipping bbox calculation when generating the entire planet"
+  fi
 else
-  echo "====> : Skipping bbox calculation when generating the entire planet"
+  echo "====> : Bounding box is set in .env file"
 fi
 
 echo " "