Git Doesn’t Track File Renames (And How It Fakes It)¶
| git |
Ever used git mv to rename a file? Many people assume it creates special rename metadata in Git’s object database. Here’s the surprise: it doesn’t. Git has no concept of a “rename” operation at all.
Instead, Git uses content similarity detection algorithm. When you run git log or git diff, Git analyzes the content of deleted and added files on-the-fly. If two files are similar enough (≥50% by default), Git displays them as a rename. If not, you see them as separate delete and create operations.
In this post, we’ll see three scenarios with different similarity percentages, learn how to adjust Git’s detection threshold using the -M flag, and understand why git mv is just a convenience wrapper with no special powers.
1. How Git Stores Renames¶
Git doesn’t track renames explicitly. According to official documentation, Git detects renames post-hoc by analyzing content similarity:
- ≥50% similar (default): Git shows as renamed
- <50% similar: Git shows as deleted + created
1.1. What about git mv?¶
git mv is just a convenience command that does this:
# These are equivalent:
git mv old.txt new.txt
# Same as:
mv old.txt new.txt
git rm old.txt
git add new.txt
Both produce identical Git objects - no rename metadata is stored.
Let’s demonstrate this with a practical example. We’ll create an empty test repository:
DEMO_REPO="git-rename-test-repo"
mkdir "$DEMO_REPO"
cd "$DEMO_REPO"
git init
git config user.name "Demo User"
git config user.email "demo@example.com"
2. SCENARIO 1: Move file without changes¶
# Creating file1.txt with 10 lines...
cat > file1.txt << 'EOF'
Line 01: This is the first line of the file
Line 02: This is the second line of the file
Line 03: This is the third line of the file
Line 04: This is the fourth line of the file
Line 05: This is the fifth line of the file
Line 06: This is the sixth line of the file
Line 07: This is the seventh line of the file
Line 08: This is the eighth line of the file
Line 09: This is the ninth line of the file
Line 10: This is the tenth line of the file
EOF
git add file1.txt
git commit -m "Add file1.txt"
[main (root-commit) 776edcb] Add file1.txt
1 file changed, 10 insertions(+)
create mode 100644 file1.txt
# Moving file1.txt to docs/file1.txt (no content change)...
mkdir docs
git mv file1.txt docs/file1.txt
git commit -m "Move file to docs folder"
[main d37b953] Move file to docs folder
1 file changed, 0 insertions(+), 0 deletions(-)
rename file1.txt => docs/file1.txt (100%)
2.1. Git detection result¶
git show --stat -M HEAD
commit d37b9531cbf0e5bbe499fd2cbd49e365685d053e (HEAD -> main)
Author: Demo User <demo@example.com>
Date: Sat Jan 31 07:49:56 2026 +0100
Move file to docs folder
file1.txt => docs/file1.txt | 0
1 file changed, 0 insertions(+), 0 deletions(-)
Result: Git detects this as a rename (R100 = 100% similarity). All 10/10 lines unchanged = 100% > 50% threshold.
3. SCENARIO 2: Move with minor changes¶
# Creating file2.txt with 10 lines...
cat > file2.txt << 'EOF'
Line 01: This is the first line of the file
Line 02: This is the second line of the file
Line 03: This is the third line of the file
Line 04: This is the fourth line of the file
Line 05: This is the fifth line of the file
Line 06: This is the sixth line of the file
Line 07: This is the seventh line of the file
Line 08: This is the eighth line of the file
Line 09: This is the ninth line of the file
Line 10: This is the tenth line of the file
EOF
git add file2.txt
git commit -m "Add file2.txt"
[main cb90460] Add file2.txt
1 file changed, 10 insertions(+)
create mode 100644 file2.txt
# Moving to subdir/file2.txt and changing 2 lines (80% similarity)...
mkdir -p subdir
cat > subdir/file2.txt << 'EOF'
Line 01: This is the first line of the file
Line 02: This line has been MODIFIED
Line 03: This is the third line of the file
Line 04: This is the fourth line of the file
Line 05: This is the fifth line of the file
Line 06: This is the sixth line of the file
Line 07: This is the seventh line of the file
Line 08: This is the eighth line of the file
Line 09: This is the ninth line of the file
Line 10: This line has also been MODIFIED
EOF
git rm file2.txt
rm 'file2.txt'
git add subdir/file2.txt
git commit -m "Move and modify 2 lines"
[main 7f9839c] Move and modify 2 lines
1 file changed, 2 insertions(+), 2 deletions(-)
rename file2.txt => subdir/file2.txt (80%)
3.1. Git detection result¶
git show --stat -M HEAD
commit 7f9839c33fb19397f9354ea4f8c17ba4e48141ee (HEAD -> main)
Author: Demo User <demo@example.com>
Date: Sat Jan 31 07:57:53 2026 +0100
Move and modify 2 lines
file2.txt => subdir/file2.txt | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
Result: Git detects this as a rename (R80 = 80% similarity). Changed 2/10 lines, so 8/10 lines unchanged = 80% > 50% threshold.
4. SCENARIO 3: Move with major changes¶
# Creating file3.txt with 10 lines...
cat > file3.txt << 'EOF'
Line 01: This is the first line of the file
Line 02: This is the second line of the file
Line 03: This is the third line of the file
Line 04: This is the fourth line of the file
Line 05: This is the fifth line of the file
Line 06: This is the sixth line of the file
Line 07: This is the seventh line of the file
Line 08: This is the eighth line of the file
Line 09: This is the ninth line of the file
Line 10: This is the tenth line of the file
EOF
git add file3.txt
git commit -m "Add file3.txt"
[main f43b480] Add file3.txt
1 file changed, 10 insertions(+)
create mode 100644 file3.txt
# Moving to newdir/file3.txt and changing 8 lines (20% similarity)...
mkdir -p newdir
cat > newdir/file3.txt << 'EOF'
Line 01: COMPLETELY DIFFERENT CONTENT HERE
Line 02: COMPLETELY DIFFERENT CONTENT HERE
Line 03: This is the third line of the file
Line 04: COMPLETELY DIFFERENT CONTENT HERE
Line 05: COMPLETELY DIFFERENT CONTENT HERE
Line 06: COMPLETELY DIFFERENT CONTENT HERE
Line 07: COMPLETELY DIFFERENT CONTENT HERE
Line 08: COMPLETELY DIFFERENT CONTENT HERE
Line 09: COMPLETELY DIFFERENT CONTENT HERE
Line 10: This is the tenth line of the file
EOF
git rm file3.txt -q
git add newdir/file3.txt
git commit -m "Move and rewrite most content"
[main 963ddde] Move and rewrite most content
2 files changed, 10 insertions(+), 10 deletions(-)
delete mode 100644 file3.txt
create mode 100644 newdir/file3.txt
4.1. Git detection result¶
git show --stat -M HEAD
commit 963dddea7bfe74d02b9873c59faae60a9c7132fe (HEAD -> main)
Author: Demo User <demo@example.com>
Date: Sat Jan 31 08:40:39 2026 +0100
Move and rewrite most content
file3.txt | 10 ----------
newdir/file3.txt | 10 ++++++++++
2 files changed, 10 insertions(+), 10 deletions(-)
Result: Git does NOT detect this as a rename. Changed 8/10 lines, so only 2/10 lines unchanged = 20% < 50% threshold. Git shows ‘file3.txt’ deleted and ‘newdir/file3.txt’ created.
5. Key Takeaways¶
Git’s rename detection is a powerful feature that works entirely through content similarity analysis:
- No metadata stored: Git treats
git mvandmv + git rm + git addidentically - Default 50% threshold: Works well for most use cases
- Adjustable sensitivity: Use
-M<percentage>to tune detection (e.g.,-M30%for aggressive,-M90%for strict) - Post-hoc analysis: Rename detection happens when you run
git log,git show, orgit diff, not during commit
Appendix: Full commit history¶
A.1. With rename detection (default 50% threshold)¶
View full commit history
git log --oneline --stat -M --reverse
776edcb Add file1.txt
file1.txt | 10 ++++++++++
1 file changed, 10 insertions(+)
d37b953 Move file to docs folder
file1.txt => docs/file1.txt | 0
1 file changed, 0 insertions(+), 0 deletions(-)
cb90460 Add file2.txt
file2.txt | 10 ++++++++++
1 file changed, 10 insertions(+)
7f9839c Move and modify 2 lines
file2.txt => subdir/file2.txt | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
f43b480 Add file3.txt
file3.txt | 10 ++++++++++
1 file changed, 10 insertions(+)
963ddde (HEAD -> main) Move and rewrite most content
file3.txt | 10 ----------
newdir/file3.txt | 10 ++++++++++
2 files changed, 10 insertions(+), 10 deletions(-)
A.2. Experiment with different thresholds¶
You can adjust Git’s rename detection sensitivity using the -M flag. Let’s see how different thresholds affect the detection of our three scenarios:
A.2.1. With 30% threshold (-M30%)¶
Lower threshold = more aggressive rename detection, but File3 (20% similarity) is still below the 30% threshold:
View output with -M30%
git log --oneline --name-status -M30% --reverse
776edcb Add file1.txt
A file1.txt
d37b953 Move file to docs folder
R100 file1.txt docs/file1.txt
cb90460 Add file2.txt
A file2.txt
7f9839c Move and modify 2 lines
R080 file2.txt subdir/file2.txt
f43b480 Add file3.txt
A file3.txt
963ddde (HEAD -> main) Move and rewrite most content
D file3.txt
A newdir/file3.txt
A.2.2. With 90% threshold (-M90%)¶
Higher threshold = stricter rename detection. File2 (80% similarity) no longer detected as a rename:
View output with -M90%
git log --oneline --name-status -M90% --reverse
776edcb Add file1.txt
A file1.txt
d37b953 Move file to docs folder
R100 file1.txt docs/file1.txt
cb90460 Add file2.txt
A file2.txt
7f9839c Move and modify 2 lines
D file2.txt
A subdir/file2.txt
f43b480 Add file3.txt
A file3.txt
963ddde (HEAD -> main) Move and rewrite most content
D file3.txt
A newdir/file3.txt
A.3. Show detailed diff with rename detection¶
View detailed diff output
git log -p -M --reverse
commit 776edcb0641eb4fdde03c54c051695b79dfdf4a8
Author: Demo User <demo@example.com>
Date: Sat Jan 31 07:49:43 2026 +0100
Add file1.txt
diff --git a/file1.txt b/file1.txt
new file mode 100644
index 0000000..941da65
--- /dev/null
+++ b/file1.txt
@@ -0,0 +1,10 @@
+Line 01: This is the first line of the file
+Line 02: This is the second line of the file
+Line 03: This is the third line of the file
+Line 04: This is the fourth line of the file
+Line 05: This is the fifth line of the file
+Line 06: This is the sixth line of the file
+Line 07: This is the seventh line of the file
+Line 08: This is the eighth line of the file
+Line 09: This is the ninth line of the file
+Line 10: This is the tenth line of the file
commit d37b9531cbf0e5bbe499fd2cbd49e365685d053e
Author: Demo User <demo@example.com>
Date: Sat Jan 31 07:49:56 2026 +0100
Move file to docs folder
diff --git a/file1.txt b/docs/file1.txt
similarity index 100%
rename from file1.txt
rename to docs/file1.txt
commit cb904608397555d6dd1810e6d1985c86d8d7092c
Author: Demo User <demo@example.com>
Date: Sat Jan 31 07:54:10 2026 +0100
Add file2.txt
diff --git a/file2.txt b/file2.txt
new file mode 100644
index 0000000..941da65
--- /dev/null
+++ b/file2.txt
@@ -0,0 +1,10 @@
+Line 01: This is the first line of the file
+Line 02: This is the second line of the file
+Line 03: This is the third line of the file
+Line 04: This is the fourth line of the file
+Line 05: This is the fifth line of the file
+Line 06: This is the sixth line of the file
+Line 07: This is the seventh line of the file
+Line 08: This is the eighth line of the file
+Line 09: This is the ninth line of the file
+Line 10: This is the tenth line of the file
commit 7f9839c33fb19397f9354ea4f8c17ba4e48141ee
Author: Demo User <demo@example.com>
Date: Sat Jan 31 07:57:53 2026 +0100
Move and modify 2 lines
diff --git a/file2.txt b/subdir/file2.txt
similarity index 80%
rename from file2.txt
rename to subdir/file2.txt
index 941da65..a651b2e 100644
--- a/file2.txt
+++ b/subdir/file2.txt
@@ -1,5 +1,5 @@
Line 01: This is the first line of the file
-Line 02: This is the second line of the file
+Line 02: This line has been MODIFIED
Line 03: This is the third line of the file
Line 04: This is the fourth line of the file
Line 05: This is the fifth line of the file
@@ -7,4 +7,4 @@ Line 06: This is the sixth line of the file
Line 07: This is the seventh line of the file
Line 08: This is the eighth line of the file
Line 09: This is the ninth line of the file
-Line 10: This is the tenth line of the file
+Line 10: This line has also been MODIFIED
commit f43b4801b0a1073245cf18b6461d10fc82024f99
Author: Demo User <demo@example.com>
Date: Sat Jan 31 08:39:44 2026 +0100
Add file3.txt
diff --git a/file3.txt b/file3.txt
new file mode 100644
index 0000000..941da65
--- /dev/null
+++ b/file3.txt
@@ -0,0 +1,10 @@
+Line 01: This is the first line of the file
+Line 02: This is the second line of the file
+Line 03: This is the third line of the file
+Line 04: This is the fourth line of the file
+Line 05: This is the fifth line of the file
+Line 06: This is the sixth line of the file
+Line 07: This is the seventh line of the file
+Line 08: This is the eighth line of the file
+Line 09: This is the ninth line of the file
+Line 10: This is the tenth line of the file
commit 963dddea7bfe74d02b9873c59faae60a9c7132fe
Author: Demo User <demo@example.com>
Date: Sat Jan 31 08:40:39 2026 +0100
Move and rewrite most content
diff --git a/file3.txt b/file3.txt
deleted file mode 100644
index 941da65..0000000
--- a/file3.txt
+++ /dev/null
@@ -1,10 +0,0 @@
-Line 01: This is the first line of the file
-Line 02: This is the second line of the file
-Line 03: This is the third line of the file
-Line 04: This is the fourth line of the file
-Line 05: This is the fifth line of the file
-Line 06: This is the sixth line of the file
-Line 07: This is the seventh line of the file
-Line 08: This is the eighth line of the file
-Line 09: This is the ninth line of the file
-Line 10: This is the tenth line of the file
diff --git a/newdir/file3.txt b/newdir/file3.txt
new file mode 100644
index 0000000..bd0c679
--- /dev/null
+++ b/newdir/file3.txt
@@ -0,0 +1,10 @@
+Line 01: COMPLETELY DIFFERENT CONTENT HERE
+Line 02: COMPLETELY DIFFERENT CONTENT HERE
+Line 03: This is the third line of the file
+Line 04: COMPLETELY DIFFERENT CONTENT HERE
+Line 05: COMPLETELY DIFFERENT CONTENT HERE
+Line 06: COMPLETELY DIFFERENT CONTENT HERE
+Line 07: COMPLETELY DIFFERENT CONTENT HERE
+Line 08: COMPLETELY DIFFERENT CONTENT HERE
+Line 09: COMPLETELY DIFFERENT CONTENT HERE
+Line 10: This is the tenth line of the file