Add the ability to use source in commit message

[olblak]

Fix #1129

Updatecli relies on Go template to read Updatecli manifest and works in two steps:

1. Load manifest based on information known at start time and ignore information known a runtime such as source output
2. Then after each source/condition/target, Updatecli re-load the manifest.

The problem here is that the manifest spec is correctly updated but not the pipeline.
The current pull request add a new function named "pipeline.Update() error" to do exactly that

Test

To test this pull request, you can run the following commands:
I used the following manifest for my tests

Manifest

name: Test Commit message
scms:
  default:
    kind: git 
    spec:
      url: https://github.com/updatecli-test/cargo-lab.git
      commitmessage:
        title: 'Bump to {{ source "default" }}'
      branch: main

sources:
  default:
    kind: jenkins
    spec:
      ##release: stable
      release: weekly
  test3:
    name: 'update cargo to {{ source "default" }}'
    kind: shell
    dependson:
      - default
    spec:
      command: "true"

conditions:
  test4:
    name: 'update cargo to {{ source "default" }}'
    disablesourceinput: true
    kind: shell
    spec:
      command: "true"

targets:
  test5:
    name: 'update cargo to {{ source "default" }}'
    disablesourceinput: true
    kind: file
    scmid: default
    spec:
      file: "Cargo.toml"    

Then I run the following commands

go build -o bin/updatecli
./bin/updatecli apply --config updatecli/updatecli.d/testcommit.yaml --push=false --debug
cd /tmp/updatecli/github_com_updatecli-test_cargo-lab_git/ 
git log --pretty=format:%s -n1
# Return chore: Bump to 2.389

Additional Information

Tradeoff

Potential improvement

The HCL library provides a way to use both information known a start time and runtime and seems to be a better approach https://pkg.go.dev/github.com/hashicorp/hcl/v2

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