examples-from-user-filed-issues.md: cover corrupt trees too

Handling corrupt trees is similar to handling corrupt commits, but the
editing is slightly different, so just add an example so that we cover
both types of corruption.

Signed-off-by: Elijah Newren <[email protected]>

Author: newren

Documentation/examples-from-user-filed-issues.md

@@ -88,7 +88,7 @@ git filter-repo \
 Replace "stuff" in any commit message with "task".
 
 ```
-git-filter-repo --message-callback 'return message.replace(b"stuff", b"task")'
+git filter-repo --message-callback 'return message.replace(b"stuff", b"task")'
 ```
 
 ## Only keep files from two branches
@@ -245,12 +245,21 @@ git filter-repo --refs main~5..main --commit-callback '
 
 First, run fsck to get a list of the corrupt objects, e.g.:
 ```
-$ git fsck
+$ git fsck --full
 error in commit 166f57b3fbe31257100361ecaf735f305b533b21: missingSpaceBeforeDate: invalid author/committer line - missing space before date
+error in tree c15680eae81cc8539af7e7de766a8a7c13bd27df: duplicateEntries: contains duplicate file entries
 Checking object directories: 100% (256/256), done.
 ```
 
-Then print out that object literally to a temporary file:
+Odds are you'll only see one type of corruption, but if you see
+multiple, you can either do multiple filterings, or create replacement
+objects for all the corrupt objects (both commits and trees), and then
+do the filtering.  Since the method for handling corrupt commits and
+corrupt tress is slightly different, I'll give examples below for each.
+
+### Handling repository corruption -- commit objects
+
+Print out the corrupt object literally to a temporary file:
 ```
 $ git cat-file -p 166f57b3fbe31257100361ecaf735f305b533b21 >tmp
 ```
@@ -266,7 +275,8 @@ Initial
 ```
 
 Edit that file to fix the error (in this case, the missing space
-between author email and author date):
+between author email and author date).  In this case, it would look
+like this after editing:
 
 ```
 tree e1d871155fce791680ec899fe7869067f2b4ffd2
@@ -276,7 +286,7 @@ committer My Name <[email protected]> 1673287380 -0800
 Initial
 ```
 
-Save the updated file, then use `git-replace` to make a replace reference
+Save the updated file, then use `git replace` to make a replace reference
 for it.
 ```
 $ git replace -f 166f57b3fbe31257100361ecaf735f305b533b21 $(git hash-object -t commit -w tmp)
@@ -294,6 +304,62 @@ Note that if you have multiple corrupt objects, you only need to run
 filter-repo once; that is, so long as you create all the replacements
 before you run filter-repo.
 
+### Handling repository corruption -- tree objects
+
+<!-- GitHub customer example -->
+
+Print out the corrupt object literally to a temporary file:
+```
+$ git cat-file -p c15680eae81cc8539af7e7de766a8a7c13bd27df >tmp
+```
+
+Taking a look at the file would show, for example:
+```
+$ cat tmp
+100644 blob cd5ded43e86f80bfd384702e3f4cc7ce42de49f9	.gitignore
+100644 blob 226febfcc91ec2c166a5a06834fb47c3553ec469	README.md
+100644 blob e69de29bb2d1d6434b8b29ae775ad8c2e48c5391	src
+040000 tree df2b8fc99e1c1d4dbc0a854d9f72157f1d6ea078	src
+040000 tree 99d732476808176bb9d73bcbfe2505e43d65cb4f	t
+```
+
+Edit that file to fix the error (in this case, removing either the `src`
+file (blob) or the `src` directory (tree)).  In this case, it might look
+like this after editing:
+
+```
+100644 blob cd5ded43e86f80bfd384702e3f4cc7ce42de49f9	.gitignore
+100644 blob 226febfcc91ec2c166a5a06834fb47c3553ec469	README.md
+040000 tree df2b8fc99e1c1d4dbc0a854d9f72157f1d6ea078	src
+040000 tree 99d732476808176bb9d73bcbfe2505e43d65cb4f	t
+```
+
+Save the updated file, then use `git mktree` to turn it into an actual
+tree object:
+```
+$ git mktree <tmp
+ace04f50a5d13b43e94c12802d3d8a6c66a35b1d
+```
+
+Now use the output of that command to create a replacement object for
+the original corrupt object:
+```
+git replace -f c15680eae81cc8539af7e7de766a8a7c13bd27df ace04f50a5d13b43e94c12802d3d8a6c66a35b1d
+```
+
+Then remove the temporary file `tmp` and run `filter-repo` to consume
+the replace reference and make it permanent:
+
+```
+$ rm tmp
+$ git filter-repo --proceed
+```
+
+As mentioned with corrupt commit objects, if you have multiple corrupt
+objects, as long as you create all the replacements for those objects
+first, you only need to run filter-repo once.
+
+
 ## Removing all files with a backslash in them
 
 <!-- https://github.com/newren/git-filter-repo/issues/427 -->