Fix IndexOutOfRangeException in CreateFromGit when parsing malformed Git external links

[Copilot]

Description

Fixes #3068

The TfsGitRepositoryInfo.CreateFromGit method crashes with IndexOutOfRangeException when processing Git external links that don't contain the expected three-part format (projectId%2frepoId%2fcommitId). The method was accessing array elements without bounds checking.

// Before: crashes on malformed links
string[] bits = Regex.Split(guidbits, "%2f", RegexOptions.IgnoreCase);
repoID = bits[1];  // IndexOutOfRangeException if bits.Length < 2
commitID = bits[2]; // IndexOutOfRangeException if bits.Length < 3

// After: validates before access
if (bits.Length < 3)
{
    Log.Warning("GitRepositoryInfo: Invalid Git external link format...");
    return null;
}
repoID = bits[1];
commitID = bits[2];

Changes:

• Added bounds validation requiring minimum 3 array elements before accessing bits[1] and bits[2]
• Returns null with warning log for malformed links instead of throwing
• Removed unreachable else branch after validation
• Added unit tests covering valid (3+ parts) and invalid (0-2 parts) link formats

Things to be aware of

• Logging uses serilog - All Logging should be in the format "My message that contains {item} and {item2}", item, item2! Do not use $"My message that contains {item} and {item2}" to pass text into the log strings as this disables Serilog's ability to pass that data as telemetry to Application Insights and for log highlighting.

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How Has This Been Tested?

• Unit tests added for valid 3-part links
• Unit tests added for valid links with extended commit IDs (4+ parts)
• Unit tests added for malformed links (1-2 parts)
• CodeQL security analysis (0 vulnerabilities)
• Full solution build verification

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules

Original prompt

---

This section details on the original issue you should resolve

<issue_title>System.IndexOutOfRangeException when cretaing links with CreateFromGit</issue_title>
<issue_description>

Discussed in #3068

^{Originally posted by ptc-96 November 21, 2025}
Hello,

I am performing a migration and I have encountered an error while migrating git links.

{"Timestamp":"2025-11-20T13:14:26.7544653+01:00","Level":"Error","MessageTemplate":"Sy**stem.IndexOutOfRangeException: Index was outside the bounds of the array.** \r\n   
at MigrationTools.Tools.TfsGitRepositoryInfo.CreateFromGit(ExternalLink gitExternalLink, IList 1 possibleRepos) in D:\\a\\azure-devops-migration-tools\\azure-devops-migration-tools\\src\\MigrationTools.Clients.TfsObjectModel\\Tools\\TfsGitRepositoryInfo.cs:line 97\r\n   
at MigrationTools.Tools.TfsGitRepositoryInfo.Create(ExternalLink gitExternalLink, IList 1 possibleRepos, TfsChangeSetMappingTool tfsChangeSetMappingTool, String workItemSourceProjectName) in D:\\a\\azure-devops-migration-tools\\azure-devops-migration-tools\\src\\MigrationTools.Clients.TfsObjectModel\\Tools\\TfsGitRepositoryInfo.cs:line 31\r\n   
at MigrationTools.Tools.TfsGitRepositoryTool.Enrich(TfsProcessor processor, WorkItemData sourceWorkItem, WorkItemData targetWorkItem) in D:\\a\\azure-devops-migration-tools\\azure-devops-migration-tools\\src\\MigrationTools.Clients.TfsObjectModel\\Tools\\TfsGitRepositoryTool.cs:line 109\r\n   
at MigrationTools.Processors.TfsWorkItemMigrationProcessor.ProcessWorkItemLinks(WorkItemData sourceWorkItem, WorkItemData targetWorkItem) in D:\\a\\azure-devops-migration-tools\\azure-devops-migration-tools\\src\\MigrationTools.Clients.TfsObjectModel\\Processors\\TfsWorkItemMigrationProcessor.cs:line 686\r\n   
at MigrationTools.Processors.TfsWorkItemMigrationProcessor.<ProcessWorkItemAsync>d__31.MoveNext() in D:\\a\\azure-devops-migration-tools\\azure-devops-migration-tools\\src\\MigrationTools.Clients.TfsObjectModel\\Processors\\TfsWorkItemMigrationProcessor.cs:line 581",

I've checked that some of the LinkedArtifactUri values of the Git links are not in the expected legacy format:
vstfs:///Git/Commit/_repoId_**%2f**_commitId_
but instead use the newer Azure DevOps format:
vstfs:///Git/Commit/_projectName_/_repoName_/_commitId_

This causes the tool to fail when trying to parse and construct the Git link.
<img width="1502" height="223" alt="image" src="https://github.com/user-attachments/assets/07489056-8b5b-43d2-b005-703ae0204580" />

Suggestion:
If supporting the new URI formats is not possible at this time, would it be feasible to at least catch this exception so the migration process does not stop entirely?

Thanks!

</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes System.IndexOutOfRangeException when cretaing links with CreateFromGit #3069

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