FormChooseCommit & Rebase onto: Display only potential commits (#11703)

to display only the commits the user could act on
to avoid selecting a commit that has no effects
and so that the commit choice is not overwhelming
and user has less data to process to find commit he wants

+ manage edge case where the user could try to do a rebase onto
where that's not possible with only one commit to rebase and displayed in the grid:
no commits are selected and so parents links must be hidden
because not initialized and a click on it (if user really want to do strange things)
could lead to a crash.

GitUI/CommandsDialogs/FormRebase.cs

@@ -1,5 +1,6 @@
 using GitCommands;
 using GitCommands.Git;
+using GitExtUtils;
 using GitExtUtils.GitUI.Theming;
 using GitUI.HelperDialogs;
 using GitUIPluginInterfaces;
@@ -408,7 +409,24 @@ private void btnChooseFromRevision_Click(object sender, EventArgs e)
                 AppSettings.ShowStashes = false;
                 ObjectId firstParent = UICommands.Module.RevParse("HEAD~");
                 string preSelectedCommit = !string.IsNullOrWhiteSpace(txtFrom.Text) ? txtFrom.Text : firstParent?.ToString() ?? string.Empty;
-                using FormChooseCommit chooseForm = new(UICommands, preSelectedCommit, showCurrentBranchOnly: true);
+
+                string mergeBaseCommitId = null;
+
+                if (!string.IsNullOrWhiteSpace(cboBranches.Text))
+                {
+                    try
+                    {
+                        ObjectId commit1 = UICommands.Module.RevParse(cboBranches.Text);
+                        ObjectId commit2 = UICommands.Module.RevParse("HEAD");
+                        mergeBaseCommitId = UICommands.Module.GetMergeBase(commit1, commit2)?.ToString();
+                    }
+                    catch (Exception)
+                    {
+                        // if an exception occurs, display whole history
+                    }
+                }
+
+                using FormChooseCommit chooseForm = new(UICommands, preSelectedCommit, showCurrentBranchOnly: true, lastRevisionToDisplayHash: mergeBaseCommitId);
                 if (chooseForm.ShowDialog(this) == DialogResult.OK && chooseForm.SelectedRevision is not null)
                 {
                     txtFrom.Text = chooseForm.SelectedRevision.ObjectId.ToShortString();

GitUI/HelperDialogs/FormChooseCommit.cs

@@ -12,11 +12,16 @@ private FormChooseCommit(GitUICommands commands)
             InitializeComplete();
         }
 
-        public FormChooseCommit(GitUICommands commands, string? preselectCommit, bool showArtificial = false, bool showCurrentBranchOnly = false)
+        public FormChooseCommit(GitUICommands commands, string? preselectCommit, bool showArtificial = false, bool showCurrentBranchOnly = false, string? lastRevisionToDisplayHash = null)
             : this(commands)
         {
             revisionGrid.MultiSelect = false;
             revisionGrid.ShowUncommittedChangesIfPossible = showArtificial;
+            if (lastRevisionToDisplayHash is not null)
+            {
+                revisionGrid.SetLastRevisionToDisplayHash(lastRevisionToDisplayHash);
+            }
+
             if (showCurrentBranchOnly)
             {
                 revisionGrid.ShowCurrentBranchOnly();
@@ -83,7 +88,12 @@ private void revisionGrid_SelectionChanged(object sender, EventArgs e)
         {
             IReadOnlyList<GitRevision> revisions = revisionGrid.GetSelectedRevisions();
 
-            if (revisions.Count != 1)
+            bool singleCommitSelected = revisions.Count == 1;
+            labelParents.Visible = singleCommitSelected;
+            linkLabelParent.Visible = singleCommitSelected;
+            linkLabelParent2.Visible = singleCommitSelected;
+
+            if (!singleCommitSelected)
             {
                 return;
             }

GitUI/UserControls/RevisionGrid/FilterInfo.cs

@@ -194,6 +194,12 @@ public bool HasRevisionFilter
                 || ShowSimplifyByDecoration;
         }
 
+        /// <summary>
+        /// The hash of the last revision to display (i.e. the oldest one displayed at the bottom).
+        /// This hash is used to query history only until this given commit.
+        /// </summary>
+        public string LastRevisionToDisplayHash { get; internal set; }
+
         /// <summary>
         /// Disables all active filters.
         /// CurrentBranch and Reflog are not disabled.
@@ -483,6 +489,11 @@ private void GetBranchRevisionFilter(ArgumentBuilder filter, Lazy<ObjectId?> cur
                 }
             }
 
+            if (!string.IsNullOrWhiteSpace(LastRevisionToDisplayHash))
+            {
+                filter.Add($"...{LastRevisionToDisplayHash}");
+            }
+
             return;
 
             // git-log filters add implicit /* to the filters, unless there are wildcard characters in the ref name

GitUI/UserControls/RevisionGrid/RevisionGridControl.cs

@@ -1952,6 +1952,11 @@ public void ShowCurrentBranchOnly()
             PerformRefreshRevisions();
         }
 
+        public void SetLastRevisionToDisplayHash(string hash)
+        {
+            _filterInfo.LastRevisionToDisplayHash = hash;
+        }
+
         public void ShowRevisionFilterDialog()
         {
             using FormRevisionFilter form = new(UICommands, _filterInfo);