From f36e2a9b8adc656c5ec35f01454e59225221aa66 Mon Sep 17 00:00:00 2001
From: Ricardo Lopes <ricardo.lopes@appliedblockchain.com>
Date: Sat, 29 Jul 2023 12:32:46 +0100
Subject: [PATCH 1/3] add dynamic base-revision

---
 src/commands/set-parameters.yml  |  3 ++-
 src/jobs/filter.yml              |  3 ++-
 src/scripts/create-parameters.py | 10 ++++++++++
 3 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/src/commands/set-parameters.yml b/src/commands/set-parameters.yml
index 9481431..726d118 100644
--- a/src/commands/set-parameters.yml
+++ b/src/commands/set-parameters.yml
@@ -8,7 +8,8 @@ parameters:
     default: "main"
     description: >
       The revision to compare the current one against for the purpose
-      of determining changed files.
+      of determining changed files. Supports passing environment variables,
+      eg. $CIRCLE_BRANCH, or shell script evaluating to a string, eg. $(echo "dev").
   mapping:
     type: string
     default: ""
diff --git a/src/jobs/filter.yml b/src/jobs/filter.yml
index 7d478e9..5bd9813 100644
--- a/src/jobs/filter.yml
+++ b/src/jobs/filter.yml
@@ -22,7 +22,8 @@ parameters:
     default: "main"
     description: >
       The revision to compare the current one against for the purpose
-      of determining changed files.
+      of determining changed files. Supports passing environment variables,
+      eg. $CIRCLE_BRANCH, or shell script evaluating to a string, eg. $(echo "dev").
   mapping:
     type: string
     default: ""
diff --git a/src/scripts/create-parameters.py b/src/scripts/create-parameters.py
index 7f404a1..b0379ab 100644
--- a/src/scripts/create-parameters.py
+++ b/src/scripts/create-parameters.py
@@ -23,6 +23,15 @@ def merge_base(base, head):
     capture_output=True
   ).stdout.decode('utf-8').strip()
 
+def eval_base(base):
+  if base.startswith('$'):
+    return subprocess.run(
+      ['sh', '-c', f"echo {base}"],
+      capture_output=True
+    ).stdout.decode('utf-8').strip()
+  
+  return base
+
 def parent_commit():
   return subprocess.run(
     ['git', 'rev-parse', 'HEAD~1'],
@@ -112,6 +121,7 @@ def is_mapping_line(line: str) -> bool:
   return not (is_comment_line or is_empty_line)
 
 def create_parameters(output_path, config_path, head, base, mapping):
+  base = eval_base(base) # Evaluate base revision if it is an environment variable or script
   checkout(base)  # Checkout base revision to make sure it is available for comparison
   checkout(head)  # return to head commit
   base = merge_base(base, head)

From 50629c29e69880719773dec21546fd2a520b37a5 Mon Sep 17 00:00:00 2001
From: Ricardo Lopes <ricardo.lopes@appliedblockchain.com>
Date: Tue, 1 Aug 2023 17:17:23 +0100
Subject: [PATCH 2/3] add fallback value if base evals null

---
 src/scripts/create-parameters.py | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/scripts/create-parameters.py b/src/scripts/create-parameters.py
index b0379ab..9d3a09e 100644
--- a/src/scripts/create-parameters.py
+++ b/src/scripts/create-parameters.py
@@ -25,11 +25,11 @@ def merge_base(base, head):
 
 def eval_base(base):
   if base.startswith('$'):
-    return subprocess.run(
+    value = subprocess.run(
       ['sh', '-c', f"echo {base}"],
       capture_output=True
     ).stdout.decode('utf-8').strip()
-  
+    return 'main' if value == '' else value
   return base
 
 def parent_commit():

From 247d3832111ac96942db793a69855250cd1efbab Mon Sep 17 00:00:00 2001
From: Ricardo Lopes <ricardo.lopes@appliedblockchain.com>
Date: Tue, 1 Aug 2023 17:18:27 +0100
Subject: [PATCH 3/3] adds before set-params script config

---
 src/jobs/filter.yml | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/src/jobs/filter.yml b/src/jobs/filter.yml
index 5bd9813..5ada1e7 100644
--- a/src/jobs/filter.yml
+++ b/src/jobs/filter.yml
@@ -60,6 +60,10 @@ parameters:
     description: >
       Pick a specific cimg/python image variant:
       https://hub.docker.com/r/cimg/python/tags
+  before_set_params_script:
+      default: ""
+      description: Script to run before set-parameters step. Used to load custom environment variables.
+      type: string
 
 steps:
   - checkout
@@ -70,6 +74,14 @@ steps:
       steps:
         - attach_workspace:
             at: << parameters.workspace_path >>
+  - when:
+      condition:
+        not:
+          equal: ["", << parameters.before_set_params_script >>]
+      steps:
+        - run:
+            name: Before set-parameters script
+            command: << parameters.before_set_params_script >>
   - set-parameters:
       base-revision: << parameters.base-revision >>
       mapping: << parameters.mapping >>