Add --version flag showing git tag and sha

```
│  Agent powering down. Goodbye!
│
│  Interaction Summary
│  Session ID:                 66751fe9-fcad-4221-a90a-34d84d303807
│  Tool Calls:                 15 ( ✓ 15 x 0 )
│  Success Rate:               100.0%
│  User Agreement:             100.0% (15 reviewed)
│  Code Changes:               +81 -0
│
│  Performance
│  Wall Time:                  9m 51s
│  Agent Active:               2m 50s
│    » API Time:               1m 40s (58.6%)
│    » Tool Time:              1m 10s (41.4%)
│
│
│  Model Usage                 Reqs   Input Tokens   Cache Reads  Output Tokens
│  ────────────────────────────────────────────────────────────────────────────
│  gemini-2.5-flash-lite          2          2,635             0            199
│  gemini-3-pro-preview          15         54,232       163,544          1,828
│
│  Savings Highlight: 163,544 (74.2%) of input tokens were served from the cache, reducing costs.
```

build.rs

@@ -0,0 +1,42 @@
+use std::process::Command;
+
+fn main() {
+    // Only re-run if .git state changes
+    println!("cargo:rerun-if-changed=.git/HEAD");
+    println!("cargo:rerun-if-changed=.git/refs/tags");
+
+    let output = Command::new("git")
+        .args(["describe", "--tags", "--exact-match"])
+        .output();
+
+    let version = if let Ok(output) = output {
+        if output.status.success() {
+            // Exact tag match
+            String::from_utf8(output.stdout).unwrap().trim().to_string()
+        } else {
+            // Not an exact match, construct version string
+            let tag_output = Command::new("git")
+                .args(["describe", "--tags", "--abbrev=0"])
+                .output()
+                .expect("Failed to execute git describe");
+            
+            let sha_output = Command::new("git")
+                .args(["rev-parse", "--short", "HEAD"])
+                .output()
+                .expect("Failed to execute git rev-parse");
+
+            if tag_output.status.success() && sha_output.status.success() {
+                let tag = String::from_utf8(tag_output.stdout).unwrap().trim().to_string();
+                let sha = String::from_utf8(sha_output.stdout).unwrap().trim().to_string();
+                format!("{}-g{}", tag, sha)
+            } else {
+                // Fallback if git fails or no tags
+                "unknown".to_string()
+            }
+        }
+    } else {
+        "unknown".to_string()
+    };
+
+    println!("cargo:rustc-env=GIT_VERSION={}", version);
+}

src/main.rs

@@ -8,6 +8,7 @@ use tracing::{Level, error, info, instrument, warn};
 
 #[derive(Parser, Debug)]
 #[command(name = "gitea-mirror")]
+#[command(version = env!("GIT_VERSION"))]
 #[command(about = "Syncs Git repositories to Gitea based on a TOML config.")]
 struct Args {
     /// Path to the TOML configuration file.

vibe_coding_log/session_2026_01_10_version_flag.md

@@ -0,0 +1,38 @@
+# Session Log: Add Version Flag
+
+**Date**: Saturday, January 10, 2026
+**Model**: Gemini (CLI Agent)
+**Goal**: Add a `--version` flag that displays the git tag and short SHA.
+**Outcome**: Implemented dynamic versioning using `build.rs` and `clap`.
+
+---
+
+## Transcript Summary
+
+### 1. Version Flag Implementation
+
+**User**: Requested a `--version` flag that output the latest git tag. If the current commit is not exactly on a tag, it should append the short SHA (e.g., `v0.6-gd8a9fc`).
+
+**Agent Action**:
+1.  Analyzed `Cargo.toml` and `src/main.rs`.
+2.  Created a `build.rs` script to handle the logic:
+    *   Tries `git describe --tags --exact-match`.
+    *   If that fails, tries `git describe --tags --abbrev=0` (latest tag) combined with `git rev-parse --short HEAD` (current SHA).
+    *   Sets the `GIT_VERSION` environment variable.
+3.  Modified `src/main.rs`:
+    *   Updated the `clap` `Args` struct to use `#[command(version = env!("GIT_VERSION"))]`.
+4.  Verified the output using `cargo run -- --version`.
+
+### 2. Verification
+
+**User**: Implicitly relied on agent verification.
+
+**Agent Action**:
+1.  Ran `cargo run -- --version` -> Output: `gitea-mirror v0.6-gf13906d` (correct format).
+2.  Created a temporary tag `v0.7.0-test`, verified output was `gitea-mirror v0.7.0-test`, then deleted the tag.
+3.  Ran `cargo clippy` (clean).
+4.  Committed changes including the new `build.rs` and updated `src/main.rs`.
+
+## Final State
+
+The application now supports `gitea-mirror --version` which dynamically reports the git version at build time.