♻️ support subset + simplify retrieval + template

This commit builds on 1c16800 and:
- simplifies the retrieval (via git) to dynamically identify the full list of
  deployments. Notably it no longer relies on munging command output
- supports providing a subset of the deployments via an environment variable

It also adds a new function that is lightweight and just prints out the
configured URL as a simple template for testing and adapting

Testing done:
- ran the template function above

```
./e-mission-py.bash bin/historical/migrations/all_deployments_template.py
Connecting to database URLmongodb://localhost:27017/openpath_prod_nc_transit_equity_study
Running print_connect_url for ebikegj on DB ebikegj
Config file not found, returning a copy of the environment variables instead...
Retrieved config: {'DB_HOST': 'mongodb://localhost:27017/openpath_prod_ebikegj', 'DB_RESULT_LIMIT': None}
Connecting to database URL mongodb://localhost:27017/openpath_prod_ebikegj
Connecting to database URLmongodb://localhost:27017/openpath_prod_ebikegj
Running print_connect_url for cortezebikes on DB cortezebikes
Config file not found, returning a copy of the environment variables instead...
Retrieved config: {'DB_HOST': 'mongodb://localhost:27017/openpath_prod_cortezebikes', 'DB_RESULT_LIMIT': None}
Connecting to database URL mongodb://localhost:27017/openpath_prod_cortezebikes
Connecting to database URLmongodb://localhost:27017/openpath_prod_cortezebikes
Running print_connect_url for dcebike on DB dcebike
Config file not found, returning a copy of the environment variables instead...
Retrieved config: {'DB_HOST': 'mongodb://localhost:27017/openpath_prod_dcebike', 'DB_RESULT_LIMIT': None}
Connecting to database URL mongodb://localhost:27017/openpath_prod_dcebike
Connecting to database URLmongodb://localhost:27017/openpath_prod_dcebike
Running print_connect_url for washingtoncommons on DB washingtoncommons
Config file not found, returning a copy of the environment variables instead...
Retrieved config: {'DB_HOST': 'mongodb://localhost:27017/openpath_prod_washingtoncommons', 'DB_RESULT_LIMIT': None}
```
- ran the template function above with an overridden `PROD_LIST`. Note that the
  first two entries are from final values set to the DB_HOST variable before
  the program terminated previously. We may want to unset the variable before
  the program ends

```
$ export PROD_LIST='cortezebikes,fortmorgan'
$ ./e-mission-py.bash bin/historical/migrations/all_deployments_template.py
Config file not found, returning a copy of the environment variables instead...
Retrieved config: {'DB_HOST': 'mongodb://localhost/openpath_prod_nrel_commute', 'DB_RESULT_LIMIT': None}
Connecting to database URL mongodb://localhost/openpath_prod_nrel_commute
PROD_LIST: ['cortezebikes', 'fortmorgan']
Running print_connect_url for cortezebikes on DB cortezebikes
Config file not found, returning a copy of the environment variables instead...
Retrieved config: {'DB_HOST': 'mongodb://localhost:27017/openpath_prod_cortezebikes', 'DB_RESULT_LIMIT': None}
Connecting to database URL mongodb://localhost:27017/openpath_prod_cortezebikes
Connecting to database URLmongodb://localhost:27017/openpath_prod_cortezebikes
Running print_connect_url for fortmorgan on DB fortmorgan
Config file not found, returning a copy of the environment variables instead...
Retrieved config: {'DB_HOST': 'mongodb://localhost:27017/openpath_prod_fortmorgan', 'DB_RESULT_LIMIT': None}
Connecting to database URL mongodb://localhost:27017/openpath_prod_fortmorgan
Connecting to database URLmongodb://localhost:27017/openpath_prod_fortmorgan

```

bin/historical/migrations/_common.py

@@ -2,29 +2,30 @@
 import subprocess
 import importlib
 import logging
+import tempfile
+import time
 
 import emission.core.get_database as edb
 
-DB_HOST_TEMPLATE = "mongodb://localhost:27017/openpath_prod_REPLACEME"
+DB_HOST_TEMPLATE = os.environ.get('DB_HOST_TEMPLATE', "mongodb://localhost:27017/openpath_prod_REPLACEME")
 
-proc = subprocess.run(
-      'rm -rf nrel-openpath-deploy-configs && ' +
-      'git clone --no-checkout https://github.com/e-mission/nrel-openpath-deploy-configs.git && ' +
-      'cd nrel-openpath-deploy-configs && ' +
-      'git ls-tree -r --name-only HEAD | grep configs/',
-      shell=True,
-      capture_output=True,
-      text=True)
-filenames = proc.stdout.replace("configs/", "").split("\n")
+if 'PROD_LIST' in os.environ:
+    PROD_LIST=os.environ['PROD_LIST'].split(",")
+else:
+    with tempfile.TemporaryDirectory() as tmpdirname:
+        print(f"created {tmpdirname=} to find list of configs")
+        os.chdir(tmpdirname)
+        proc = subprocess.run(
+              f"git clone https://github.com/e-mission/nrel-openpath-deploy-configs.git", shell=True)
+        filenames = os.listdir(f"nrel-openpath-deploy-configs/configs/")
 
-PROD_LIST = [
-    fname.split(".")[0]
-    for fname in filenames
-      if fname and 'dev-' not in fname and 'stage-' not in fname
-]
+    PROD_LIST = [
+        fname.split(".")[0]
+        for fname in filenames
+          if fname and 'dev-' not in fname and 'stage-' not in fname
+    ]
 print(f"PROD_LIST: {PROD_LIST}")
 
-
 def run_on_all_deployments(fn_to_run):
     """
     Run the given function on the database for each deployment by setting the

bin/historical/migrations/all_deployments_template.py

@@ -0,0 +1,8 @@
+import emission.core.get_database as edb
+
+from _common import run_on_all_deployments
+
+def print_connect_url():
+    print("Connecting to database URL"+edb.url)
+
+run_on_all_deployments(print_connect_url)