feat(librarian): rename source_commit_hash to commit_hash (#2224)

For now we will support the old field as well until currently onboarded
languages have a chance to source the new field instead.

Fixes: #2107

Author: codyoss

doc/language-onboarding.md

@@ -272,14 +272,14 @@ global file edits. The libraries that are being released will be marked by the `
           "subject": "add new UpdateRepository API",
           "body": "This adds the ability to update a repository's properties.",
           "piper_cl_number": "786353207",
-          "source_commit_hash": "9461532e7d19c8d71709ec3b502e5d81340fb661"
+          "commit_hash": "9461532e7d19c8d71709ec3b502e5d81340fb661"
         },
         {
           "type": "docs",
           "subject": "fix typo in BranchRule comment",
           "body": "",
           "piper_cl_number": "786353207",
-          "source_commit_hash": "9461532e7d19c8d71709ec3b502e5d81340fb661"
+          "commit_hash": "9461532e7d19c8d71709ec3b502e5d81340fb661"
         }
       ],
       "apis": [

internal/conventionalcommits/conventional_commits.go

@@ -64,7 +64,10 @@ type ConventionalCommit struct {
 	// IsNested indicates if the commit is a nested commit.
 	IsNested bool `yaml:"-" json:"-"`
 	// SHA is the full commit hash.
+	// Deprecated: use CommitHash instead.
 	SHA string `yaml:"-" json:"source_commit_hash,omitempty"`
+	// CommitHash is the full commit hash.
+	CommitHash string `yaml:"-" json:"commit_hash,omitempty"`
 	// When is the timestamp of the commit.
 	When time.Time `yaml:"-" json:"-"`
 }
@@ -218,6 +221,7 @@ func parseSimpleCommit(commitPart commitPart, commit *gitrepo.Commit, libraryID
 			IsBreaking: header.IsBreaking || footerIsBreaking,
 			IsNested:   commitPart.isNested,
 			SHA:        commit.Hash.String(),
+			CommitHash: commit.Hash.String(),
 			When:       commit.When,
 		})
 	}